This is the cast type skill for healing spells.
The in game help reads:
Skill duration: random. Type of skill : spell casting skill (arcane skill). Affecting stats: None. It uses no endurance points. One of the more benevolant types of magic, is the magic which is used to heal one's self or others. Not many things, once killed, are of any use to anyone, so keeping things alive was one of the first forms of magic that was utilized. Originally starting as witch-doctors in various tribes, the art of healing through magic has evolved to a very refined art. No town within the realms is without a local healer. It is a very dangerous world, so the art of healing has been practiced and refined through the ages. In order to use healing magic effectively, some knowledge of the nature of this type of magic is required.