How does rage work?
Rage is used to launch yourself into battle with a ferocity that few other classes can match. It is represented by the red bar near your portraitand unlike health, rage does not increase as you gain levels and is always measured on a scale of 0-100.
Also unlike health, rage does not replenish naturally. You build it up by dealing and taking damage. The specifics of this depend on what skills you are using and what combat stance you are in. When you are out of combat, your rage will gradually decrease until it reaches 0, as you "cool off" and your anger seeps away. Because of this, it often makes sense to rush from one fight to the next as soon as possible to keep your rage (as long as you're not too badly hurt, of course).
Once you have built up some rage, you can use it to power a wide variety of special attacks and abilities. These include powerful attacks that increase the damage you deal, shouts that improve the abilities of your party members, and many others.