An object layer can be used to help build up a map with visual meta-objects that convey information about the map to viewers (e.g. someone viewing a map in a report).
Objects in an object layer do not move relative to the map, but to the viewing area of the map window, so, when an object is added, actions such as panning or zooming to not cause the objects to move, they will stay in place. Objects can be moved and certain objects can be resized as required.
Below is a sample map with some added objects to illustrate its purpose: