Been doing lots of extensive searching but can not find any any explanation as to what SE & DE are for, how to use them and why
Review this Wiki page: http://www.digi.com/wiki/developer/index.php/Understanding_XBee_EndPoints
They are not easy to use unless you are writing your own device code, and don’t make the mistake of thinking of them as just like UDP/IP port numbers.
I believe the ‘pure’ answer in ZigBee context would be the example of a wall switch with 3 physical buttons/switches, therefore 3 sets of the ‘data clusters’ related to switches. These would be 3 distinct end-points.