Stealth is an ability that allows players or mobs to sneak around undetected. Most notably a rogue's ability, it is also available (as Prowl) to druids when using their Cat Form, as well as hunter cat pets. Unlike invisibility, anybody has a chance to detect an enemy in stealth mode. The chance of detection increases as you get closer, but also depends on the viewing angle (stand right in front of an enemy and you can guarantee they'll see you), the relative levels, and any perception or subtlety modifiers.