About Map: holds information of last modification, ratings, and comments.
Show Contents of Map: defines the map locator PINS used. Here you can check and uncheck the boxes located to the left of the map locator PIN descriptions. Essentially you can toggle items in the map on and off as you would like to see them.
Map Legend: In the ArcGIS online edition does not function as a traditional legend. For the ArcGIS version of a legend use the "Show Contents of Map" function.