HP — Hit Points
How much damage a character or creature can take before it is knocked out, dying or defeated.
Hit Points (HP) measure how much harm a character or creature can take. Damage lowers them; healing and rest bring them back up, but never above the maximum. What happens when they run out depends on the ruleset and the Game Master (GM): it may mean unconscious, dying or defeated, not necessarily dead. Shown as current / maximum, e.g. 7 / 12.
In Fantasy RPG
In Fantasy RPG a monster at 0 HP is defeated. When a player character drops to 0 HP the GM makes the call: dead, unconscious, stabilised or ignore it. A short rest heals some HP and a long rest heals fully.