Kashyyyk, the jungle planet home of the Wookiees, is quite unlike any of the other worlds in Star Wars Galaxies. While all the other worlds are based on a philosophy of open travel, where you can go from one point to any other pretty much at will (assuming you can survive), on Kashyyyk, much of the terrain is impassible. This means that to pass from one zone to another, you have to go to a specific gate point. In fact, before you can enter most Kashyyyk zones for the first time, you must usually first earn the right to enter by completing a specific mission.
Furthermore, in addition to being gated, many of the Kashyyyk zones are instanced. This means that the game can create multiple identical copies of the zone map, so that when a group enters the zone, they’ll have it all to themselves. Other groups that may be playing in the same zone at the same time will have their own, private maps to adventure on.
Some of the instanced zones will spawn a separate instance for each individual group that enters. Others will admit multiple groups, but are designed for a certain optimum maximum population. When you enter such a zone, the game will give you a choice of several instances, showing you the current population of each one, and allow you to choose which one you’ll adventure in. At this time, the game does not prohibit you from entering a zone even if it’s population is “full,” but you’re advised to avoid full instances if possible, for an optimal playing experience.