MapServer MapManager is a desktop application designed by DMS to compose maps to be served by MapServer.
When rendering the map MapServer uses map configuration files (MapFiles) which contain connection information for each data source and the commands to set the visual representation. The commands are composed using the MapServer Object Model and consist of various object types like layers, classes, styles and labels.
MapFiles are text files and can be edited manually according to the map file specification. Editing text files can be handy in some situations, it's not the easiest way to construct good looking maps to be rendered by MapServer.
The purpose of MapManager is to make this easy by providing a user interface to configure MapFiles as well as give an instant view of the map when any of the parameters are changed. There is no more requirement that every MapServer user understands how to compile MapFiles using text editors any more.