Healing is an ability a Caster has. It is the ability heal injuries and wounds. Normally, a Caster doesn't get this power unless they're a Thaumaturge. When someone is hurt, a Thaumaturge usually is able to just touch them per-say and they're healed. Ryan Duchannes was able to heal Ethan Wate and Lena Duchannes. John Breed gained this power after bumping into a random Thaumaturge with his power absorption and was able to heal Liv.