Overlays do not work on the default Map. They only work on Google Maps. 

• Title is the Name of the map as it is displayed in the Map Menu
• Type can not be changed.
• Overlay is the url to the KML or KMZ overlay you want to add to your system. Overlays override and centering and zoom settings you may have entered into the Map Setup Tab.

You can delete or edit maps by going to the Admin->System Setup->List Pages.

Here are some KML overlays you can use:

• https://earthquake.usgs.gov/earthquakes/feed/v1.0/summary/1.0_week_age_link.kml
• https://www.nhc.noaa.gov/xgtwo/gtwo_atl.kmz
• http://www.portlandoregon.gov/scripts/911incidents-kml_link.cfm

Please feel free to add any other overlays you feel would be usefull in the comments below.