Its like a cheat code list built into the game.
You run the trainer launcher program before you load the game.
Pick which game you are about to play out of the trainer list.
And then you select the cheats you want to be activated.
Its more in depth than a cheat code though. You can do a lot
more serious stuff. Like in example... infinite grenades in halo 2...
theres no cheat code for that.