This device was one of those that worked with your Nintendo Entertainment System. However, it did NOT have the Nintendo Seal of Quality™.
I have heard several accounts of Nintendo consoles becoming "addicted" to the Game Genie, where the unit ceases to function without the Genie plugged in, whether the cheats were actually being used or not.
I have also heard several accounts of users having to "jam it in", but being completely unaware that it was ruining their consoles.