Hit Points otherwise best known as HP, H Points, Health, and Health Points, is a status or measure of how many points you still have remaining in your green health bar. Hit Points decrease by receiving damage from enemies. If a player's HP drops down to zero, they will become dead with options to choose:
Local Revive: Will teleport with Full Health at beginning of instance or at local traveling priest
Revive Here: 60 second cooldown but can revive in same spot but with minimal HP.
Every player has a amount of maximum HP, which is determined by stats, the gears equipped, other bonuses such as Secret Stones or Enchantment Cards, Food and Drinks, Eidolon Buffs and the level you are currently at. There are several ways to increase the maximum amount of HP.
Hit Points can be both dropped and healed back. There are several methods of healing, including using the auto-potion feature, healing skills, a specialized healing class such as Bard or using a Nocturnal Weapon.