The heart of a mud is the map: the world the mud represents. This serves as the stage upon which all action takes place. Unlike other forms of virtual communities, like web boards, live chat areas, and so on, muds rely on an attempt to represent virtual space. Elements are arranged in mimicry of geographical relationships. Sometimes, the actual spatiality of the world represented bears no resemblance to natural physics, but the portrayal is nonetheless spatial.

That said, there are still two principal methods of representing and codifying the virtual space within a mud. One of them is arguably better suited to a graphical medium, and the other better suited to text. These two approaches are really all about how the data that makes up the map is segmented. They can be described as a room-based model, in which the map is partitioned into sub-maps which have clear point-to-point exits leading to another “room” located elsewhere; and continuous maps, which do not have said “exit” points, but which instead allow movement from map to map anywhere along the continuous border of the two distinct spaces.