The Action Replays are accessories, not games

There's the Game Action Replay released in the US, which is likely the one you are trying to find info on (the one with the transparent cartridge).  This one allows you to save at any point in any game (I think it also allows you to do slow-mo & turbo if I remember right).

Then there's the Pro Action Replay released in Germany and the UK, which is very much like a Game Genie, allowing you to enter codes to change certain aspects of a game.  On top of that, it also acts as a regional converter, allowing you to play NTSC games on PAL machines, and possibly vice versa as well.