As far as im aware its like a diagnostic tool that runs from a laptop to your car, reads fault codes etc etc..
Been looking for this myself and cant seem to find it anywhere, thinks its a small fortune to buy lol
 
Oh right... Cheers mate.

Am away to have a scan on ebay myself, Know doubt we will have to get the right one for are model lol.

Yea seems a very handy thing to have like.