A console emulator is a program that allows a computer or modern console (cross-console emulation) to emulate a video game console. Emulators are most often used to play older video games on personal computers and modern video game consoles, but they are also used to translate games into other languages, to modify (or hack) existing games, and in the development process of homebrewed demos and new games for older systems.

 

ROM stands for Read Only Memory. Contained in the ROM is the game. It's that simple. Any game you can imagine can be a rom, as well as hacks, and even custom made games. For reading this, here's something special: