Ref Emulating, masta could have possibly been a bit clearer, but ill try and explain it a bit better.
Alot of people think the job of an emulator is to run a game. That is incorrect.
An emulator emulates the hardware of a computer, whether it be a desktop computer, laptop, phone, console, arcade and fruit machines, emulators are available to emulate the hardware inside these machines.
Because this hardware is emulated, it allows you to run media designed to be run on that hardware.
Unfortunately this process is extremely difficult. We are only now at a stage where you can play Playstation 2 games smoothly on a High End PC. Luckily, smartphone technology has advanced at a faster rate than computers do, with them all readying having a 1Ghz+ cpu, so we can emulate hardware like a Playstation on our smartphones, however still as you said, its not 100% smooth.