[SIZE=2]Quite simply game shark codes are codes used specifically with the Game Shark,a "game enhancer" made by InterAct.Without this the codes are useless.
These codes are put in before the game loads and can change specific bits of coding to make the game easier or harder (infinite weapons,infinite health,one shot kills,etc.).
You can find out more about it at the official web site.I'd put the address here but it isn't allowed under the rules of the forum.They own the domain name for GameShark so the address is very simple to figure out.[/SIZE]