Mame | 2003 Reference Set - Mame 0.078 Roms- Chds...

ROMs are files that contain the game data from the original arcade game boards. These files are essentially digital copies of the games' programming and graphics. CHDs, on the other hand, are files that contain data from the hard disk drives used in some arcade games. CHDs are used to emulate the games that rely on hard disk technology, which was introduced in the late 1980s.