Healing is a special skill of waterbending that allows waterbenders to heal others. They do this by drawing on the life-giving properties of water to heal many types of physical wounds, some illnesses, and even pain caused by mental stress. Any skilled waterbender can perform this art, but mastery over it requires practise.
However, there are limits to what can be healed. For example, waterbenders cannot heal fatal wound, or make scars disappear. It is also apparent that healing cannot undo a blockage to a bender's chi by chi blockers, and in addition, a healer can detect where chi flow is blocked. Water from the Spirit Oasis, however, has special properties and can heal wounds that regular water cannot, such as said permanent damage or permanent scars.