Heal Over Time (HoTs): Heal over time spells restore a total amount of hit points over several seconds. These types of healing spells usually require little mana, spell points, or whatever type of casting currency exists in the game. HoTs are likely the most efficient heal spell to use on another player, but they do not handle burst damage well. This type of healing is strictly used to counteract steady damage taken over a period of time. Examples: Renew (WoW Priest), Rejuvenation (WoW Druid)
Heal plus HoT: This is simply a HoT with a small direct heal given to the target of the spell. This deals with burst damage a bit better than a HoT. While this spell will not heal as much damage up front as a direct heal, it usually heals for more over time. Examples: Regrowth (WoW Druid), Dark Elixir (WAR Zealot), Restore Essence (WAR Disciple of Khaine)
Reactive heals: These heals are placed on a player and will heal a certain amount of damage as it is taken by that player. These heals are usually placed on a player before battle and are excellent for dealing with the alpha strike (the initial burst of damage) when attacking an opponent. Examples: Bestowal of Vitae (EQII Templar and Inquisitor)
Spread heal: This is the “smart” heal, and it is a group heal. The spread heal heals a specific amount of damage across the entire group, but it assigns more healing to those who are most damaged first. Examples: Spread Heal (DAoC Healer)
Vampiric heal: These heals require the healer to be doing some sort of damage. Then a percentage of the damage done is translated into heals for the healer’s chosen target. These are often small amounts of healing that can add up over time. Examples: Bleed Fer’ Me (WAR Shaman), Rend Soul (WAR Disciple of Khaine)
Simply knowing the types of heals that exist and identifying them quickly will allow you to quickly assimilate to any MMO where you want to be healing. While some games have truly unique healing systems, most follow a general pattern that can be easily discerned and maximized. Keep these heals in mind, and practice using them appropriately as you move through whatever world you and your teammates are currently exploring.