2000/2001
1999/2000
The rear plate.
You can change your registration number e.g. MY08CAR, but not your VIN or other numbers. You may not change your registration to a plate of a newer year due to misidentification eg if you have a 2004 car, you cannot put a 2006 plate on it, but you can put older plates on eg a 2002 plate on a 2004 car.
2011
the rear plate
sep 2011
biusxxsd
If you're asking about where to put your sticker on the license plate than that would be the rear plate.
In most areas, you need to renew your license plate sticker every year. This allows states to keep vehicle records and registration as current as possible.
If you mean this in car/vehicle terms then I'm sure its the registration plate.....Vehicle Registration Mark
Spain