The BBC Micro is a computer made by Acorn. Rather like the Apple II in the US, it was mostly used as an educational computer to learn how to program in schools and also because it was expensive to buy meaning very few home owners had access to the machine.
Please see here for more info.
MAME supports the BBC Micro and is well supported thanks to the work of Nigel Barnes who has preserved this system and the Acorn Electron.
BeebEm is an emulator that supports every model of the BBC Micro. One may not understand how to load tapes or disks at first because it requires a key command, and also you must load a "boot" and a "start" rom in disk 0 and disk 1 respectively in order to load your game.