handler?
you mean handle.
a handle is ANYTHING that is not a Boolean, String, Integer, Real, or Code
a widget is a HANDLE that is not in the Player ( force, player, etc. ) or Trigger category
( someone correct me if im wrong on the widget )
therefore, any unit is a widget, so we can say
unit u == widget u <--- this will be true if widget u was assigned the same object as unit u
unit u == handle u <--- this will be true if handle u was assigned the same object as unit u
widget u == handle u <--- this will always be true
in Common.j, you can look all this upp
eg. Type Widget extends Handle
etc.