A healer is someone who purports to aid recovery from ill health, including alleged faith healers.
Some practitioners of alternative health practices seek to restrict the term to themselves, claiming they work with the natural recuperative self-healing properties of the body, which they term vitalism. They assert that other approaches work against the body's own healing abilities.
In MMORPG is the healer the common name for character classes who are responsible for keeping the other party members alive by casting healing spells while they are injured.