Healing was a super power that allowed people to heal another person who may have been shot or stabbed, or had something else happen to them that would have been a serious enough to be a fatal injury.
When someone used such an ability, this would often bring instant relief to the person who experienced the healing, and sometimes it could give temporary pain to the healer. This was usually not enough to kill the healer, otherwise that would be a terrible super power!
This ability should not be confused with Accelerated Healing, because that ability was only useful if the person who was shot or stabbed had the ability, not if someone else with no super powers had been. In other words, if a person without that power received a fatal injury, they would just die, as a person with Accelerated Healing would not be able to help them at all.