A scooter is a two-wheeled motor vehicle with a step-through frame. Many modern scooters have their engines located forward of the seat and affixed to the frame.

In contrast to most motorcycles, scooters generally have bodywork, including a front leg shield and body that conceals all or most of the mechanical parts. There is often some integral storage space, either under the seat, built into the front leg shield, or both.

Most modern motor scooters have smaller wheels than motorcycles, between eight and 12 inches (20-28 cm) in diameter (though maxi- and big-wheel scooters may have larger wheels). Most scooters have smaller engines than motorcycles (between 30 cc and 250 cc with a single cylinder, though larger models have twin cylinder 400 to 650 cc. motors).

Most countries have no legal definition for "scooter". In general, 50 cc and under scooters are classified in most states and countries as a moped and are subject to reduced safety restrictions and licensing fees. 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 ccs.