A Nintendo Entertainment System ROM file (.nes) is a digital copy of a game cartridge for the classic NES console. It contains all the data necessary to emulate and play the game on a computer or other device. These files are essentially memory dumps of the game's program code, graphics, and audio data. Emulators interpret this data, simulating the NES hardware and allowing users to experience the games on modern systems. The legality of possessing and distributing NES ROMs is complex and depends on copyright laws and whether the user owns the original game cartridge. While many ROMs are available online, downloading and using them without owning the original game may be considered copyright infringement. NES ROMs are a popular way to preserve and enjoy classic games, but users should be aware of the legal implications before downloading or sharing them.