To a cartographer, a map is a divided area with boundaries between different regions. For a graph theorist, a map corresponds to a graph. When two regions share a border, they are considered connected. For a map on a planar region, such a graph is called a planar graph. In this Demonstration, click the internal black edges to change the map.
Graphs drawn by this method are called maps, rectangular embeddings, or box-rectangular drawings. Architects call them floor plans. Many different puzzle types, such as crosswords and Slitherlink, use edge boundaries of this type.