Health is the indicator of whether or not a character is alive or dead. It is a core battle mechanic of Dungeon Defenders II.
Health will deplete as the character takes damage. Once your health reaches zero, your character will die and re-spawn after a set amount of time. Hero health is displayed in the top left of the HUD. Enemies, Defenses and Map Objectives also have health bars which deplete as they take damage, and can be viewed by hovering the crosshair over them.
Defense Health Bars
Defense Health bars indicate how many health points your defense has. Most defenses have health points like the hero does, and when depleted, it is destroyed. This includes blockades and towers. As Traps and Auras cannot be targeted by enemies, they use a charge system. When enemies activate a trap, a charge/lifespan will be consumed.