A ROM (Read-Only Memory) is a digital copy of a game that can be played on a computer or mobile device using an emulator. In the case of Pokémon Ultra Moon ROM, it's a digital version of the game that can be downloaded and played on a device that supports emulation.
Pokémon Ultra Moon is a popular role-playing game developed by Game Freak and published by Nintendo for the Nintendo 3DS. The game was released in 2017 and has since become a favorite among Pokémon fans. If you're looking to play Pokémon Ultra Moon on your computer or mobile device, you might be interested in the ROM version.