MapTool virtualizes the battle map, miniatures, and wet-erase markers. In combination with Voice over IP software this allows GMs and Players to get together virtually and interact much like they would at a session around the table.
The virtual tabletop in MapTool can do things that the classic battle map couldn’t easily do. Prepared maps from other software can just be dropped into the background and tokens moved over the top. You can also save the entire campaign at any point to resume later.