Prøv at læse denne tutorial for en forklaring:
http://www.actionscript.org/resources/articles/204/1/Using-EventDispatcher/Page1.htmlFra tutorialen:
"The event object you receive always includes a reference to the caller. This may sound a bit esoteric, if you don't understand don't lose sleep over it, but the scope in which the callback is called can be forced using a Delegate, yet you still know the original piece of code that dispatched the event. That gives you a lot of flexibility, since classes can handle events within their scope while keeping track of the real caller and all of this without ugly hacks, compiler fooling and other things that make babies cry."