A Map Overlays panel allows the user to filter a map panel's items by the area in which they are located. This panel type is only available if the dashboard contains at least one map panel that also has overlays.
The only setting is to select the map panel to which it refers. This panel will then show the area in the currently selected overlay from which the user may select or more to filter the map.
Note that when the user changes the selected overlay, this panel will be redisplayed with the new overlay's areas.