There are two sources of healing in Dungeon World: medical aid and the passage of time. Medical aid can be magical or mundane. The amount (or type) of damage healed is the reult of the item or move used.
Types of Medical Aid
Healing via Passage of Time
Whenever an adventurer spends time resting without doing anything to aggravate their wounds, they heal via the rules for Make Camp and Recover . No source of healing will restore a character's HP above their maximum. That would require an increase in Constitution score via leveling or some kind of advanced move or magic item that inceased the Maximum HP itself.
When you settle in to rest consume a ration. If you’re somewhere dangerous decide the watch order as well. If you have enough XP you may level up. When you wake from at least a few uninterrupted hours of sleep heal damage equal to half your max HP.
When you do nothing but rest in comfort and safety after a day of rest you recover all your HP. After three days of rest you remove one debility of your choice. If you’re under the care of a healer (magical or otherwise) you heal a debility for every two days of rest instead.