nissan fast is the parts software that nissan uses. there are two versions out there, the common one that covers cars up to 2001ish, and the newer one which only a few people have, but it covers all the newer model cars like the M35 and V35 aswell.
when you do a fast check you put your VIN number in the software and you can see how your car came from factory, wheather it was a turbo or not, manual or auto, what colour it was, and if it had any factory fitted options. its also good for getting part numbers.