Emulator

An emulator is itself a program that creates an extra layer between an existing computer platform (host platform) and the platform to be reproduced (target platform) .

Emulators allow software exclusive to one system to be used on another. For example, a PlayStation 2 exclusive video game could be played on a PC using an emulator. This is especially useful when the original system is difficult to obtain, or incompatible with modern equipment (e.g. old video game consoles which connect via analog outputs may be unable to connect to modern TVs which may only have digital inputs).

Sources:

"What is emulation?". Koninklijke Bibliotheek. Retrieved 2007-12-1