What is an emulator? An emulator is a program that emulates something else. For an example there are NES (Nintendo Entertainment System) emulators. An NES emulator will emulate the NES's CPU, graphics, and any other thing about the NES. Of couse it will run NES games. But you don't just stick a NES ROM into your disk drive. You may either use a game copier or there are web sites with the special ROMS. Emulators are made because you don't find old games in stores now. People just like to play those games. But since Nintendo is still in copyright you should delete the files in 24 hours. You may keep them if you have the real game though. And if you get in trouble for downloading games that you don't have don't mention me.