Interfaces, anyone got protips?

The more I read the more I am astonished at how little I know about as3.

Last night I discovered: Interfaces. It was a quick little segment in my new book and as much as it glorified it, it gave it about one page to explain itself. And one page doesn’t didn’t do it since more than half of it was spilled over by margins and code referencing.

So what I got the jist of it was that it’s used to create extensions [interfaces] between more than one class. But I still can’t grasp how this is used relative to ‘extends’ and inside packages and classes.

If anyone can give me a real world example or snippet, I’d be much appreciative.