Section "Presenting Data: Themes" introduced the concept of presentation layer. This section treats layers in more detail.

Generally speaking, layers are sets of data which together make up the contents of a Map window. Besides the presentation layer, there are also map layers, which make up the map itself and cannot be edited. In both types of layers, however, it is possible to make a number of settings that do not affect the contents of the layers, for instance to set the visibility of each layer. These settings are detailed below.