A ROM is a computer file that contains a copy of data from read-only memory. It may be a firmware, a game cartridge, or anything else on a computer. You probably know that video games were stored on cartridges in the past, but ROM files are still in use today. A modern video game cartridge contains a great deal of data. Since retro gaming consoles are now outdated, this doesn't mean that the same occurred to your favourite titles. Magic: The Gathering cards are still available as ROMs files.
They are stored in a particular format that is suitable for a certain emulator. You just have to download them on your device. However, ROM files have different extensions. There are certain formats for which only a certain emulator can open them. For example, the eighties are remembered for their popularity immediately after their release. Game consoles from this period were extremely popular with gamers!