what the heck is an emulator rom ?
An Emulator Rom is a piece of software that emulates the original operating system that a particular game was based on. There are a few good ROMs out there. MAME is a good one - it stands for Multiple Arcade Machine Emulator. Download it and you can run a lot of different arcade games on your PC.
smithmax is correct.
tiy get different types, like a ps1, ps2, gameboy and all different ones. It lets you play different types of arcade playstation etc. games on you computer.
im pretty sure its the game for the Emulator, like cartridge is to console Rom is to Emulator