I believe it's used to save your game progress. You put a memory card or whatever in there and save your progress. Not sure if it only worked for arcade or if it worked between arcade and console.
You could play NFL blitz on your N64 at home and save your team/players. You would bring your memory unit with you to the arcade and would insert it, and load up your team and stats and play with it.
You could play NFL blitz on your N64 at home and save your team/players. You would bring your memory unit with you to the arcade and would insert it, and load up your team and stats and play with it.
You could use the N64 memory card and you could create your own plays at home. Then take them to the arcade and use them on Blitz 99 against other players. Ok idea that never caught on.