A certified pre-owned vehicle is first and foremost a vehicle of the same brand as the dealer.
Certified means that it underwent a meticulous inspection of more than a hundred points. It also comes with a guarantee of at least 5.000 km, or even 40.000 km or 12 months on the important parts of your car engine, transmission, steering, electrical equipment.
To purchase a used vehicle, it is worth to compare between brands and dealers.