You just put in your disc, select the game that you want, then select the cheats. Then you just eject the cheat disc and put in the game that you want to play with the cheats enabled. The cheat screen is still up on the screen, you select START GAME, and then you can play your game with the cheats activated.
You can also play region free DVD's with it on your PS2. You put in the disc, select REGION FREE, then that means you can play region 1 DVD's, which are american, on your playstation in Europe.
Plus, you can store all your memory card saves onto your computer with the USB, so you don't have to buy another memory card. Then if you want to load up a game just download from your PC back onto your PS2. Its great if you have a game that takes up a lot of space on your memory card, and you don't play it often.