Defines the amount of actual damage that the character can sustain before being defeated.
Health is reduced based on received damage that passes through other defences and represents the ultimate resource for a character to be alive.
Health is affected by Toughness value.Almost every entity in Dungeonline has a Health value and usually when it drops to zero it means that the entity has been defeated (characters), killed (mobs), destroyed (walls, furniture), broken (items) or whatever more appropriate.
Different entity types will behave differently to Health gain and losses.
Characters are Dungeonline protagonists and as such they are privileged when Health is concerned. A character whose Health drops to zero is not definitely dead (unless it was a ranked character) but rather defeated and sent back outside the dungeon to heal back and come again another day. Characters can usually be healed during dungeon exploration and will heal between two dungeons.
Mobs are the antagonists, so they will just die when reduced to zero Health. Die or be destroyed if they were constructs or undead, but the point is the same, not coming back for them. Probably. They can be healed/repaired/restored.
Items and map elements can be damaged and destroyed when appropriate, but they'll probably not complain about it. They can be however repaired and restored.