RetroPie offers many old classic consoles through Emulation Station. In order to run these old games, you need to use what’s called an emulator. RetroPie emulators are software that allows RetroPie to act like different gaming consoles.
RetroPie uses emulators for each gaming console so we can play all different types of games on our Raspberry Pi.
The good news is you do not need to install all the emulators yourself. They are packaged into your RetroPie / Emulation Station install.
List of RetroPie Emulators
Note: Not all emulators work perfectly. Most notably Nintendo 64 games are very hard to emulate and therefor most perform poorly on RetroPie.