Normally, the starchart is an infinite plane. You can move "infinitely" to the right, into the void. A wrapped map changes this so that when you leave the Cluster to the right, you re-enter at the left, and vice versa -- as if the map were wrapped around a cylinder. Likewise, you can leave to the top and enter at the bottom.
There are at least four implementations of this concept: Sphere, PWrap and Zeus (which are host add-ons), and PHost has this built-in.
The most common wrapped map mode is a wraparound rectangle, where the universe is virtually tiled with identical copies of the map. This mode is widely supported by third-party client tools, and is very easy to play. A less common mode uses a wraparound circle, which is harder to play because the universe behind the circle is very distorted. Therefore, it is not as widely supported as the rectangle model.
