Scooter engine is either attached to the rear axle or under the seat with a continuously variable transmission transferring power to the rear wheel.
Most scooters have smaller engines than motorcycles (between 30 cc and 250 cc with a single cylinder, though some models have twin cylinder motors).
Scooters above 50 cc are generally legally considered motorcycles, though some states have an in-between definition for motorized bike for scooters and motorcycles between 50 and 150 cc.
Anyway, [link widoczny dla zalogowanych], is good for all.
In many localities, certain road motor scooters are considered by law to be in the same class as mopeds or small motorcycles and therefore they have fewer restrictions than that of larger motorcycles.