In order to manage the technical aspects of massively multiplayer online games, developers divided the world into many areas called zones. Typically there is an invisible line which, once crossed by the player, will load the next zone. These zone lines are sometimes built into doors, gates, or other objects that must be clicked in order to travel to the next area.
The concept of zones within MMO's can be exploited by players quite easily. Typically, enemies cannot cross from one zone to the next. This allows for players who are overwhelmed by enemies to escape certain death
by simply zoning into the next area. In many cases, the zone line is a popular meeting place, which creates a dangerous issue if a player in the zone is running away from a swarm of enemies and crosses the zone line to escape. The escaping player's train
of enemies immediately turn their attention to the innocent bystanders.