Radio-controlled (or R/C) vehicles are scaled-down models of full-sized vehicles.     They can be divided into two types: The "toy" category or the "hobby"  category. Control of either type is by radio transmission and power can come from one of several sources.

One way to provide power is with small but powerful electric motors that run off of rechargeable nickel-cadmium, nickel metal hydride, or lithium polymer batteries. These electric motors can be further classified as brushed or brushless.

The "nitro" vehicles use glow plug engines which are small internal combustion engines that are fueled by a special mixture of nitromethane, methanol and an oil blend of castor oil and synthetic oil.  Exceptionally large models have been introduced recently that are powered by small gasoline engines, similar to weedwhacker motors, which use a mix of oil and gasoline.

Electric powered vehicles are generally thought to be easier for the beginner or novice to work with, but can be just  as complex in their construction as the fuel-powered vehicles when you get into the higher budget and skill levels.

On-road and off-road capabilities are available in both categories. Off-road models, which are built with fully-functional off-road suspensions, can be used on various types of terrain. In comparison, on-road cars, which generally have a limited or non-existent suspension, are strictly limited to smooth, paved surfaces.

R/C vehicles use a common set of components for their control and operation. They all  require a transmitter. Control can be by  joysticks, or if in the pistol grip form, a trigger for the throttle and a wheel for turning. A receiver, which sits inside the unit, is also required. The receiver changes the radio signal sent from the transmitter into the appropriate electrical  signals for the other components of the control system. Most radio systems utilize amplitude modulation for the radio signal and the control positions are encoded with pulse width modulation. Higher end radio systems use the stronger frequency modulation and pulse code modulation.

Actions such as throttle control, braking, steering, and engaging either forward or reverse gear are controlled by either electronic controls or servomechanisms or "servos" depending on how the radio is wired up.

Electronic speed controls and servos are commanded by the receiver through pulse width modulation; pulse duration sets either the amount of current that an electronic speed control allows to flow into the electric motor or sets the angle of the servo. Rotation of the servo is mechanically changed into a force which steers the wheels most often through adjustable turnbuckle linkages. Servo savers are integrated into all steering linkages and some nitro throttle linkages. A servo saver is a flexible link between the servo and its linkage that protects the servo's internal gears from damage during impacts or stress.