An action replay is a device that inputs cheat codes into your video games, most of the time temporarly. I know how to use the DS and GBA MAX ones, but that's it. You put the game into the action replay, and then put the action replay into your game system, and then turn it on. There will be a list of things that you can put into your game, but you might want to restrict it to 5 at a time max so it doesn't overload and crash your game. The DS ones can be upgraded by downloading cheats from your computer. You can order them online at some website, but I can't remember the name right now, or you can buy it at a Best Buy or a Game Stop. Have fun Cheating!