There are three basic types of motorized scooters. These are footboard scooters (usually designed for use while standing), step-through-type motorcycles or mopeds, and mobility scooters for people with disabilities. Motorized scooters may be powered by either gas or electricity.

A motor scooter of the motorcycle or moped type is usually powered by a gasoline engine mounted at the rear of the vehicle. Although the term 'motor scooter' used to be primarily applied to motorcycles with small wheels and small engines, some manufacturers today make motor scooters with engines listed at 500cc or more. (The term cc refers to cubic centimeters of engine displacement, and can be taken as a guide to the engine's power.)

At the other end of the scale are mopeds, motor scooters with engine sizes of 49cc or less. Mopeds and motor scooters must meet various federal, state, and local requirements before they are legal for riding on the street. Mini-choppers, scooters designed to look like small 'choppers' (Harley-Davidson motorcycles), depending on engine size and other factors, may or may not be classified as mopeds. Yet another type of motor scooter, the pocket bike, is a mini motorcycle, designed for racing--not street use. Prospective buyers should check that the vehicles they are interested in will meet local requirements before agreeing to purchase one.

Ironically, perhaps, there are footboard-style scooters being sold today whose engine sizes and top speeds exceed those of mopeds. Motorized footboard scooters may have engines of 50cc, and some reach speeds of 50 miles per hour (although they more commonly go around 20 mph), whereas mopeds usually top out at 35 or 40 mph. Adults buying motorized footboard scooters for their children should therefore be aware of the scooter's engine size and top speed before buying and should always invest in all appropriate safety gear before letting their children ride one.