pvp starts at level 10 and u can que for a bg, u get more bs available as u get higher level, at the end theres like 4 bgs (called warfronts - WFs)
world pvp breaks out quite often, therell be an rift invasion (random event where mobs come out and u gotta close rifts and stop these mobs that come to destroy wardstones) in a high level place, and defiants and guardians will just start brawling.