Normally, damage describes the removal of hit points from a combatant due to hits from weapons, spells, the elements, falling, disease or breath weapon, among a host of other possibilities. When damage occurs, the amount is temporarily struck off from the combatant's maximum hit points, until such time as these points can be healed through magic or rest.
Under most conditions, damage is an expression of the wearing down of a combatant until they are reduced to negative hit points and possibly death. For situations where a lot of damage is done by a single attack, see Wounds.
For unusual circumstances where accidents or attacks cause the breaking of bone or damage to the combatant's organs, see Injury.
Attacking in Combat