From Vanguard Wiki
A benificial state in which it is more difficult for mob's (and maybe PC's also) to see you. This could be done in a fashion similar to World of Warcraft, where stealth reduces the mob's aggro radius. Or it could be implimented in a similar fashion to Everquest 2, where stealth ensures invisibilty to a mob from any distance.
The Rogue class utilizes stealth capabilities in combat.