Health in Warhammer Online is represented by health points (HP). The green bar just above the Action Points bar show the health points of the character. When the health points reach 0 your character dies. Also when you reach approximately 10% of your total health points your character is considered heavily wounded and starts to walk much more slower than the normal run speed. The health points of a character can be boosted with the wounds stat. Every wound point gives your character approximately 10 health points.
Warhammer Wiki