An emulator basically makes your computer think it is something else
For instance you could get a megadrive emulator which you'd run, and you could load files called roms, and these act as the cartridge but are just files and you could play it like you would the console, with new emulators even allowing joypads and the like.
So you could find them for anything. Though some are fake, and many are off the web now. If you downloaded roms it is only legal if you have the original cartridge and have them only for 24 hours.
There are many emulators for different consoles, megadrive, snes, nes, gameboy, etc. Some work, some dont
Hope this helps
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