Replay?

[russtafari]

Hey what's up? I hear big name people talking about they use a "replay" when they perform live. Like I heard DJ Whoo Kid talking about using one when he performs with G-Unit. He was saying how easy it was. Anyway I've tried to search for one so I can see what exactly they do and how much they are. I'm looking to do some performances very soon and think it would make the show run a lot smoother seeing as how we do not have an actual dj.

So I guess what I'm trying to say is what is a replay? Is that the official name for it? and where would I find one?

Thanks in advance!