1. The Purpose of This Article
This article will cover all the important aspects of the healing role. The information contained here will be of interest both to new players and to healing veterans.
We will not go into class-specific details. Talent specs, gemming or reforging advice are beyond the scope of this article. For such information, we recommend that you read our healing class guides.
This guide is mainly targeted at healing in a raid environment, but a lot of the things we mention will, naturally, also apply to dungeons.
2. Introduction
Healing is, in our opinion, the most stressful and difficult role to perform. There are a multitude of factors involved in performing well as a healer, but we feel that the most important ones are reactivity and class and encounter knowledge.
While part of being a great healer comes from personal skill (which we will attempt to define and dissect below), it is also extremely important to familiarise yourself with various concepts which, for the most part, are counter-intuitive.
2.1. What is Healing?
While, no doubt, some of you will find this part to be extremely basic and unneeded, we feel that, to have a proper discussion about healing, the act of healing must first be defined.
Healing is the act of using spells which restore the health of friendly players (your party or raid members) in order to help them survive the various forms of avoidable and unavoidable damage present in all PvE encounters.
This is a very basic definition, of course. In today’s raiding environment, healers also often have to dispel friendly players of various harmful debuffs (magic debuffs, curses, poisons and diseases).
Additionally, in organised raiding groups, healing is done based on assignments. This is to say, each healer will be given a specific task, such as to heal another player (for example, the tank) exclusively.
There are currently 5 classes which can perform the healing role, in World of Warcraft:
- Druids: the Restoration specialisation;
- Monks: the Mistweaver specialisation;
- Paladins: the Holy specialisation;
- Priests: the Holy and Discipline specialisations;
- Shamans: the Restoration specialisation;
10-man raids, on average, will have 3 healers assigned to keeping the entire raid alive, while 25-man raids will have around 6. There are exceptions to this, and 10-man raids often downsize to 2 healers.
Essentially, healers will be selecting damaged friendly players and casting helpful, healing spells on them.
3. The Attributes of a Great Healer
In order for this article’s structure to be easily apparent to you from the start, we will list all the attributes of a great healer. Afterwards, we will detail each of these, and provide you with tips in order to maximise your performance.
- Be able to use your character reliably and with ease, at any time during the encounter. This includes being comfortable with your user interface and your keybinds.
- Be able to anticipate what will happen in a given encounter, in terms of damage (this involves knowing the encounter mechanics), and know how to properly react to it (this involves knowing your own class).
- Understand your role within the team, and the importance of knowing your healing assignment.
As you can see, the first point relates to external factors, not necessarily related to healing. You must be extremely familiar with your user interface and with your keybinds (of which you should make extensive use).
The second point relates to encounter and class knowledge. You must be familiar with the encounter mechanics, in order to know what to expect, and you must be familiar with your own class, in order to know what spells to use in order to properly react to the damage in the fight.
The third and final point relates to understanding that you are part of a team, and that respecting your own (and other players’) assignments is crucial.
In addition to these three, main points, there are other, finer points, which you must keep in mind, such as overhealing (and how to avoid it) and mana management.
4. General Concerns
More than any other role, healing is about precision and reaction. Your ability to perform your role will be strongly affected, every step of the way, by the ease with which you can input commands to your character.
Tanks and DPS players do, sometimes, have to make split-second decisions, and these decisions can sometimes impact the outcome of the encounter. Healers, on the other hand, have to make this kind of decision every time that they use a spell.
Therefore, we feel that it is important to dedicate this section to giving you the necessary information required to tuning your character for proper performance.
4.1. Recommended Add-ons and User Interface Settings
The standard Blizzard interface has improved greatly over the years (often, by including features which were previously supported only by user-created add-ons). It is possible to perform the healing role using only this user interface, but we feel that it is far from optimal.
Below, we list three user interface elements, which we feel require further customisation. In addition to these, however, you will want to optimise your user interface in every other way, removing unnecessary items and allowing you to keep a clear view of the encounter and your raid frames.
Keep in mind that, at all times, your goal is to make your user interface aid you in completing your goals, and not have it hinder you. We feel that it is a very good investment to spend a large amount of time tweaking and tuning your interface.
4.1.1. Raid Frames
The raid frames are the most important aspect of your user interface. This is where your eyes will rest for the majority of the encounter, and you will need to be very comfortable with their appearance and layout.
There are several add-ons which present you with an improved (and highly customisable) version of the Blizzard raid frames. Before providing you with their names, we will list a few things which you should keep in mind when customising your raid frames.
- Ensure that they are large enough so that your eyes do not become tired from focusing on them at length (which you will have to do).
- Ensure that they have a position on your screen which is relatively central (either under your character or to its side).
- Ensure that they show all the relevant buffs and debuffs present on players.
- Ensure that the pet frames are also displayed (this option is usually turned off by default).
Obviously, these guidelines are subject to your own personal preference. The most important thing is that you are comfortable with your interface and that it does not hinder your actions.
We cannot stress enough how important it is that the relevant buffs and (especially) debuffs are properly displayed on the raid frames. As a healer, you will often find yourself having to dispel or cleanse raid members of various debuffs (magic, poison, curse or disease). Furthermore, and this is detailed below, you should have your dispel or cleanse ability properly keybound.
The most popular (and reliable) raid frame add-ons are:
- Grid: probably the most popular raid frame add-on available. There are many plug-ins which allow you to further enhance and customise it.
- HealBot: another popular option.
- VuhDo: a highly customisable alternative.
4.1.2. Raid Announcements
Communication is extremely important as a healer. Generally, healers have many cooldowns which affect other players (raid damage reduction cooldowns, mana regeneration cooldowns, single-target damage reduction cooldowns). It is, therefore, useful to have a means of communicating the use of these cooldowns, without choking your voice-chat medium.
We recommend Raeli’s Spell Announcer, a highly customisable add-on. We suggest that all raid-wide damage reduction cooldowns and all raid-wide mana regeneration cooldowns be announced in raid chat.
Other, single-target abilities (such as 
Pain Suppression) can simply be configured to be whispered to the targeted player.
4.1.3. Buff and Proc Monitoring
Most healing specialisations have various healing cooldowns and procs. It is essential to master these, and use them to your advantage, in order to maximise your performance.
While the Blizzard user interface has improved a lot, especially with Cataclysm, and it allows you to more easily notice various procs, we feel that this is insufficient.
We recommend WeakAuras. This highly customisable add-on allows you to create visual and auditory markers, to help you track any number of cooldowns and procs.
4.1.4. ElvUI
In all of our class guides, we recommend using ElvUI. This is a comprehensive interface add-on that will change the way your interface looks in many ways. We find that its minimalistic approach allows you to see a large amount of your screen, and focus on the important events.
4.2. Keybinding and Macros
So far, we have covered some important aspects related to add-ons and user interface settings. If you have customised your interface suitably, you should now have a good view of the encounter area and quick and easy access to your raid frames.
The next step is making sure that you can deliver your healing spells in the shortest possible amount of time. Having an excellent reaction time is an important quality of a good healer, and this is hard to accomplish without the use of keybinds.
Furthermore, selecting a target from your raid frames (by clicking it) and then using one of your spells, even through a keybinding, is not efficient. Instead, we advise you to use mouse-over macros. We discuss this in a subsequent section.
4.2.1. Keybinding
Any ability which you may need to use during combat should be keybound. This does not only refer to healing spells, but also to dispels, healing cooldowns, mana regeneration abilities, and trinkets.
Missing even a second to click an ability, as a healer, can often prove disastrous to your raid.
Moreover, as you will find in the section below, we advise you to make extensive use of mouse-over macros. Mouse-over macros, in short, allow you to cast spells on friendly players without selecting them as your target. You can simply hover your mouse over their raid frame, and use your ability.
This saves you precious time, but, as you can see, makes it impossible to hover over the raid frame and move your mouse to the action bar to click the spell. For this reason, keybinding is a mandatory practice for healers.
4.2.2. Macros
Mouse-over macros allow you to simply mouse over a friendly player (“hover” over their raid frame, for instance) and heal them without having to select them first. This can only be done if you are using keybinds, and doing so will save you precious time for each spell cast.
Below, we use the 
Heal spell to provide you with an example of a mouse-over macro:
- #showtooltip Heal
- /cast [@mouseover,exists,nodead,help,][exists,nodead,help][@player] Heal
While seemingly complicated, this macro changes your Heal spell in such a way that:
- If you are mousing over a target which exists, is not dead and is friendly, it will cast Heal on them.
- Otherwise, if your currently selected target exists, is not dead and is friendly, Heal will be cast on them instead.
- Lastly, if neither of the above two conditions are met, it will cast Heal on yourself.
You can reduce the macro to a simpler format:
- #showtooltip Heal
- /cast [@mouseover] Heal
This presents less functionality, though.
An added bonus to using mouse-over macros is that it allows you to have the boss or another add targeted (so that you can use your offensive spells on them) without it impacting your ability to heal.
4.3. Gear Optimisation
The whole theme of this section, up to this point, has been that you should put an emphasis on stability, reliability and functionality. This same idea should be reflected in your gearing.
Statistic priorities differ between healing classes, and can be affected by certain gear levels as well. The first statistic that you should aim for is Spirit. Spirit is very important for healers, as it provides mana regeneration. There is no specific point where you should stop looking for items with Spirit on them. The general guideline is that you can start looking for “caster DPS” items, with more preferable statistics, when you are comfortable with your mana regeneration rate.
This level where you have enough Spirit will vary, based, in part, on what mana regeneration cooldowns your raid has available.
After Spirit, we advise you to prefer those statistics which offer you the most reliability and precision (Haste Rating and Mastery Rating) over Critical Strike Rating, as this offers uncontrollable bursts of healing output.
The reason for this is that, as a healer, you are being constantly put under pressure to anticipate and react accordingly. In this sense, the more spell haste you have, the more reliable your healing will be. If your healing is reliant on registering critical heals, you will always be in a position, while casting a heal, to have to wonder and hope about its outcome.
For example: two players, both of whom you are assigned to heal, take two bursts of damage (each) within a 3 second interval. In order to save them from dying, you must heal each of them once before the second burst of damage hits them. If you have a lot of Haste Rating, then you will be able to reach both of them in time, even if your heal is smaller (due to lack of Mastery Rating or Spell Power from Intellect gems) and has a very low chance to be a critical strike (due to lack of Critical Strike Rating). If, instead, you have a large amount of Critical Strike Rating (hypothetically, let’s assume you are guaranteed to register a critical strike), you will heal the first player for a lot, receiving the benefit of mana-free healing, but you will not be able to cast the second heal fast enough.
Obviously, in addition to your own class’ statistic priorities, your gearing will be influenced by your healing assignment and the encounter you are progressing on.
4.4. Knowledge of the Encounter
As a healer, you have to be intimately familiar with a great part of each encounter your raid is attempting. You have to be prepared for every ability cast by the boss or an add, which has the potential to deal damage to anyone in the raid (regardless of whether this damage is avoidable or not).
A great part of being a good healer is being prepared for what is about to happen. Most boss abilities are on fixed timers or cooldowns, and will often have a predictable outcome. You must be prepared for every such ability, and already know which spell you are about to cast to heal your targets before they have taken any damage.
It is advised that, while learning encounters, you pay special attention to how much damage various abilities do, and how sustained that damage is. This will give you a good indication, for future attempts, of which spells are best used when.
For example: if you know there is a boss ability which deals a very high amount of damage (let’s say around 80% of the health of most raid members) at a specific time, and that it is not followed by any raid damage whatsoever for 30 seconds, you would make sure that everyone has enough health to survive it, and you would then go on to heal them with mana-efficient spells, allowing you to preserve your mana. If you were not familiar with the encounter mechanics, you might fail to have everyone at the minimum health threshold to survive, and you might then panic and use mana-inefficient spells trying to heal everyone up after the damage hits.
5. Healing-Specific Concerns
If you have been following this guide so far, you should have your user interface, add-ons, macros and keybinds in place. You should be comfortable with clicking your raid frames, tracking your own procs and cooldowns, and just generally using your character.
Naturally, the deeper the understanding you have of your class, the better your performance will be. This sort of coverage is beyond the scope of this article. There are, however, various aspects of playing a healer in a raid environment which are not related to class or specialisation, but rather to the healing role in general.
We have done a great deal of talking about all sorts of aspects which prepare you for healing. Now it is time to actually look what how you should heal, who you should (and should not!) heal, and what you should avoid doing.
5.1. How to Heal?
Your most basic goal, for every encounter, is that each and every one of your raid members survive until the boss is dead (or until he enrages due to insufficient DPS).
Practically, you will have to wait for raid members to suffer damage, and then use your healing spells to heal the damaged targets.
This is a simplistic look at things, and the reality is more complicated because of several factors.
- Different healing spells are suited for different situations (high mana cost and low cast time versus low mana cost and high cast time, for example).
- The damage your raid takes is not always predictable; player error will often cause random bursts of damage which you will have to heal.
- Various encounter abilities can target healers, shifting the balance of the assignments. You will need to communicate and improvise.
In order to achieve this goal, you will need to make good use of both your mana and your global cooldowns, and use the correct spells at the correct time. Let’s go into a bit of detail!
5.1.1. Mana Management
All healing classes uses mana as their main resource. Without mana, you simply cannot heal.
Mana regeneration is affected by your Spirit and by various class talents and abilities. Healers have to manage their mana for the entire duration of the encounter, and mistakes in this management can quickly lead to a wipe.
While it is beyond the scope of this article to discuss specific class abilities, all healing classes have the following types of abilities:
- a single target, small heal which costs little mana and is slow to cast;
- a single target, large heal which costs a large amount of mana and is quick to cast;
- a single target, large heal which costs a moderate amount of mana and is slow to cast;
- a single target, small heal which costs little mana and is an instant cast (it can be cast while moving);
- an area-of-effect heal.
In addition to this, each class has a few specific tools to work with.
The true skill of a healer comes from using the right heal for each situation. For example, you should use a fast and expensive heal when your target would be dead before you have the time to finish any other heal; you should use a slow and inexpensive heal when you have ample time to heal your target; you should use slow, large heals when your target is suffering sustained damage.
The idea is that, for the entire duration of the encounter, you have to strike a perfect (or near-perfect) balance between healing enough to keep your assignment alive, while not using too much mana. The only way to do this is to use the proper spells for each situation. To be able to do this, you will need an excellent understanding of your class’ abilities as well as of the encounter mechanics.
Finally, one key aspect of properly managing your mana is to ensure that you do not overheal. Overhealing is covered below, but to summarise, you should ensure that you do not expend mana on a heal which lands on a player whose health is already full (or that a great part of the heal is wasted because their health is almost full).
5.1.2. Triage
As a healer, it is your job not only to try to keep every single raid member alive, from the start of the fight until the end, but also to know when it is more profitable for your raid to let someone die so that you can better heal others (and possibly to save mana). Before we detail this further, we would like to remind you not to forget to heal yourself. It is very easy to make the mistake of trying to heal everyone else and simply overlooking your own raid (or unit) frame.
Sadly, there are times when, as a healer, you simply cannot keep everyone alive. This can be either due to encounter design (fights where the damage ramps up progressively until it becomes unhealable) or due to the mistakes which your raid makes in the execution of the fight.
When this happens, you will find yourself in a position of desperately trying to heal several low health (and dying) targets at once, and you will face being overwhelmed or running out of mana. In times like these, you will have to choose which players to heal and which players to simply let die.
While this is counter-intuitive to the nature of the healing role, it is often the only way to survive the encounter. It is impossible to state in general terms which players should be sacrificed and which players should be saved, as this can depend greatly based on the encounter.
As a rule, you should keep as many tanks alive as as are needed for the boss to be killed. Furthermore, when choosing among DPS players, those who do more damage should be preferred over others (keep in mind what stage the fight is in, though, as overall DPS numbers may not be relevant in a specific “burn phase”).
Finally, while your initial reaction might be, when seeing how difficult healing is, to try to save as many of the other healers in preference of DPS players, this is often wrong. The reason is that when a fight reaches such a critical moment, the only things which will make it easier is if the boss dies extremely quickly. Therefore, even a few seconds of another DPS player being alive can make all the difference.
5.2. Assignments
No matter what encounter your raid is progressing on, and regardless of whether it is in 10 or 25-man difficulty, your raid or healing leader will surely provide you with an assignment.
In short, you will be told who to heal, and when. For the most part, healing assignments will be simple, along the lines of “Healer #1 heals the tank, while healers #2 and #3 heal the raid.”, although sometimes the encounter may require more specific assignments.
Currently, all of the 6 healing specialisations are fairly well balanced. In the past, certain specialisations were suited to a single role (for example, Holy Paladins were exclusively tank healers during Wrath of the Lich King, while Restoration Druids were extremely potent raid healers).
Despite this balance, some specialisations shine in certain situations more than others. A good raid leader will assign specific healers to specific tasks based on the strengths and weaknesses of the healing classes (and the players playing them). If you feel that you have been given an improper assignment, or that the assignments provided, as a whole, are not satisfactory (ie., too few healers have been assigned to the raid), you should voice your concerns.
5.2.1. Tank Healing
The tanks are the only players who, regardless of encounter, take sustained damage for the entire duration of the fight. The amount of damage that they take and the frequency with which they take it varies widely from fight to fight, but in every case, the tanks must always have at least one healer assigned to them.
Most fights require two tanks, although it is possible that they will be taking damage alternatively, and not simultaneously. In any case, the amount of healing that each tank requires, based on their gear and on the encounter, is something which will have to be determined on a case-by-case basis.
You should be at least remotely familiar with the kind of tanking mechanics your assigned tank has (Paladins and Warriors have a smooth damage intake because of their blocking mechanics, Death Knights rely on self-healing, etc.).
Finally, it is very important that you communicate with the tank you are healing, so that you can both make good use of your respective cooldowns.
5.2.2. Raid Healing
Healing the raid varies widely from encounter to encounter. Some encounters present very little unavoidable raid damage, while other encounters contain heavy, sustained, unavoidable raid damage.
Based on the type of damage you are facing, you will have to adapt your healing style (and possibly your talent spec and gearing) to match it. With very few exceptions, raid healing is the task of several healers who must work together to keep the raid alive.
As a result, you must be able to communicate with your fellow healers and we advise you to set very specific healing assignments. Below are a few examples:
- Healer #1 heals the raid members (non-tanks) in Group 1 and Healer #2 heals the raid members in Group 2.
- Healer #1 starts by healing the damaged raid members, from left to right (on whatever raid-frame add-ons you are using) and Healer #2 starts healing from right to left (this is to avoid the same target within the same group being healed by multiple healers, while other targets remain unhealed).
- Healer #1 heals the players damaged by the first cast of ability X and Healer #2 heals the players subsequently damaged by ability X.
5.2.3. Cooldown Rotations
Another type of assignment which you will receive in many encounters is to use your raid-wide healing or damage reduction cooldown at a specifically determined time.
The reason for this is that there are various boss abilities which are too damaging for your raid to be able to survive without the use of cooldowns. Furthermore, these abilities will often add continuous and increasing strain on your raid’s healing, meaning that a single cooldown will not be sufficient to mitigate them.
In order for each and every damaging hit from the ability to be mitigated by some cooldown, it is important that all healers know when to use their cooldowns (so that they do not end up using two cooldowns for one ability and none for another).
When being assigned a time to use a cooldown, you should make sure of a few things:
- that you understand exactly when you need to use it, and why (timing generally needs to be very precise, with only a few seconds as a margin of error);
- that you do not (accidentally) use your cooldown on something else, before, and end up not having it available for when it is needed;
- that your cooldown does actually mitigate the damage that you are assigned to counter (your raid leader may be mistaken in how exactly your spells work);
If, for some reason, your cooldown is not available at the designated time, you should announce it to the raid ahead of time, so that they can improvise.
5.2.4. Respecting Your Assignment
One of the most sensitive issues, related to teamwork in raiding, is the ability (or inability) of healers to respect their own healing assignments.
When healing assignments are first devised, it is assumed that each healer can complete their own task without the aid of other healers. In practice, however, this is not always so. There are many factors which will cause a healer to fall behind on their assignment (latency or user interface problems, encounter mechanics, mistakes caused by the people they are assigned to heal or even by themselves). When this happens, there are two possible outcomes:
- The other healers ignore the situation, continue to only heal their assigned targets and the first healer’s target dies.
- The other healers decide to help, and therefore ignore their own assignment for a few seconds.
While the second outcome may appear to have a good chance to save lives, and the raid, this is often not the case. More often than not, what happens is that, as a result of the other healers’ reaction, they themselves will fall behind on their assignments. After this point, either chaos ensues or healers are forced to use a lot of mana-inefficient heals to catch up, thus running out of mana later on in the fight.
We advise you to stick to your assignments as much as possible. This does not meant that, if something exceptional occurs during a fight, causing one of the healers to fall behind on their assignment, they should not be helped. Indeed, great healers are those who can react to the unexpected as well as to the expected damage and situations that occur during an encounter.
What should be avoided is constantly making up for the lack of healing ability of a healer or improper healing assignments by improvising and filling other people’s roles. This type of practice is not helpful for your raid in the long-term. Instead, you should aim at correcting the underlying problems which cause you to perform someone else’s assignment. This means, the other healers should be helped to improve (or replaced) and the healing assignments themselves should be revised.
Another important reason for respecting your own healing assignment is that it ensures (in theory) equal healing of all targets. Each player in the raid has one or more healers assigned to heal them, and if assignments are respected, they will all receive heals. If you go outside of the assignments, some players will end up without any heals, while others will beoverhealed.
5.3. Overhealing
The final concept that you should be familiar with, as a healer, is overhealing. In essence, overhealing refers to when a target receives heals when their health is already at maximum. Any such healing is effectively wasted, and so is the mana that that healing cost.
We have gone through many facets of the healing role, so far, in this article. All of them are important on their own, but during all of them, you must also keep in mind that you should not overheal.
In order to avoid overhealing, you must be familiar with the amount of health that each one of your spells restores. Moreover, you should have a good understanding of the encounter mechanics, so that you know whether a damaging ability will hit the player while you are casting a heal.
Basically, you should not heal a player who is already at full health and you should only heal a damaged player with a heal which, roughly, matches the amount of missing health that they have.
Some overhealing is unavoidable, due to having to top players off in preparation for boss abilities and due to the critical heals, which will often overheal their targets. So, do not be alarmed if anywhere between 10 and 30% of your healing is overhealing. Keep in mind, though, that reducing your overhealing goes hand-in-hand with properly managing your mana, so if you are struggling for mana, you should review your overhealing.
Finally, there is one additional, less well-known, way to avoid overhealing. You should configure your raid-frames in such a way that they display any incoming heals on players (pay special attention to enable HoTs). By doing this you are able to avoid using a heal on someone who was already in the process of being healed (either through another healer’s in-progress cast or through a HoT), thus reducing your overhealing or that of the other healer.
6. Conclusions
We cannot stress enough how important it is, as a healer, to anticipate the damage which will occur and to know exactly which of the many spells in your arsenal are suitable to counter it.
Provided that you have followed this guide, and have allowed yourself sufficient time and practice to customise your user interface and familiarise yourself with your class, you should be well on your way to being a great healer!
Lastly, keep in mind that healing, more than any other role, is a team effort, and you should try to find ways to work with your teammates at all times.
We hope you have enjoyed our guide, good luck healing!
7. Changelog
- 04 Aug. 2013: Reworded a paragraph related to the importance of keybinding. In short, while we do not feel that you absolutely need to keybind in order to be a good healer, we do feel that it is a particularly advantageous practice.
Counterspell at your focus, if you have one.Otherwise, Counterspell is cast at your current target.
Glyph of Counterspell, then you can removethe /stopcasting from the macro.
Spellsteal works in the same way as the above macro for
Ice Block. Using the macro again will cancelthe spell.
Slow Fall is very useful. If you are hoveringover a party member (be it on the raid frames or on their actual character)it will cast Slow Fall on them. Otherwise, it casts it on your target,if it is friendly. If your target is not a friendly partymember, then the macro casts Slow Fall on you.
Polymorph on your focus or your current target.The first time you use this macro, the focus is set on your current target(if it is an enemy). Subsequent uses of the macro will keep castingPolymorph on your focus, unless you press alt(or whatever modifier you specify in the second line of the macro), in whichcase, the macro will set the focus on your current target before castingPolymorph on it.
Invisibility or 
Greater Invisibilityeven when casting a spell.
Blazing Speed or 
Ice Floes, depending on which you have picked.
Fireball without running the risk ofcancelling your current channel of 
Evocation.
Pyroblast without running the risk ofcancelling your current channel of 
Combustion is advised. When you criticallyhit your target with 
Ignite is high enough for Combustion,you want to cast Combustion right away and not wait for your current cast tofinish. If you wait, you run the risk that 
Presence of Mind and 
Alter Time, which areoff the global cooldown, before casting 
Meta-sockets: sockets in which a meta-gem can be inserted. Meta-gems generally offer something special when compared to other gems (such as increased movement speed or increased armor). Only head items have a meta socket.
Red, yellow and blue sockets: these coloured sockets allow any type of gem (except for meta-gems) to be inserted in them. However, matching the colour of each socket of an item will activate the socket bonus. The bonus is a moderate amount of a given statistic.
Prismatic sockets: this special type of socket allows you to obtain the socket bonus regardless of what colour gem you insert in it.
Cogwheel sockets: these sockets are only usable by Engineers. They are found on head items crafted by Engineers and they can only be filled with 
