World Bosses are slightly different from the usual Bosses that can be found in dungeons or may be needed for quests.
World Bosses can be usually found in remote locations in each zone, and respawn five hours after being killed. You might not be able to find them since they are quite popular and are renowned to drop items of Rare (blue) Item Quality.
Bosses see through invisibility talents, and crowd control skills have no effect on them.