This FAQ is an attempt to give a basic introduction to visitors who are new to emulation or to briefly answer some emulation-related questions that might arise from things on the site. Emulation is a field that is in a state of constant flux, so this FAQ will only touch on some subjects; you may find more in-depth discussions on some material on other sites.
What is emulation?
Emulation, in the most general terms, is making one thing behave like another thing. At this site, we deal with video game emulation, it's about making a computer (or some video game systems) act like a video game system or an arcade game.
Video game emulation, at it's core, is really about the nostalgia that people feel for games that have been out of circulation for a long time. Some arcade games used to be in almost every store or arcade, but are now found only in a few rare places. Likewise, older console systems sometimes stop working due to damage or age, and cannot be replaced easily. One of the purposes of video game emulation is to preserve the games for these older systems so that the games and the fun of playing them is not lost.
Of course, this is just one take on emulation. Everyone has their own opinions.
What are emulators and ROMs?
An emulator is a program that makes a computer behave like another machine. In the context of video game emulation, an emulator makes a computer behave like an arcade machine or a console gaming system for the purpose of playing games that could run on those machines or systems. Emulators, as of this time, cannot recreate the environment of a console system perfectly, so some games are not playable or have glitches.
ROMs are usually originally stored on the game cartridges or discs sold in stores. A ROM is file or series of files that contains all the information that makes up a game; all the sounds, graphics, programming code, etc. In most cases related to video game emulation, a file or files that make up a ROM are copied (or "dumped") from a game cartridge or disc. These ROM files can be played using emulators. A ROM is, basically put, a copy of a game. Not all ROMs are perfect copies of games, however. In some cases, the information is not copied correctly, and therefore the ROM is "corrupt," or unusable. There are also demo or homebrewn ROMs on the internet, which are games or programs developed independently of any video game company.