Emulators are programs that you can download over the internet that act like other machines. An emulator could act like game machines, or different computers. I have an I mac lamp G4 running mac OS X 10.4 and I loaded it with emulators of old game machines and old mac computers. This was before I knew that emulators were evil. My computer did not shut down for some reason. So a friend of mine took it to a computer fixing store to find out what was it's problem. The store had to reinstall the Mac OS X on the computer because the emulators had hurt the hard disk or hard drive. The computer runs just fine now and I will never download another emulator again because they are just bugs.