Hybrid cars are vehicles that combine two or more different power sources to propel them. The most common type of hybrid car is a series hybrid, which uses an electric motor powered by a battery pack and has no internal combustion engine. Instead, it may have a small gasoline-powered generator that charges the batteries when they run low. Other types include parallel hybrids, where both the electric motor and the internal combustion engine can provide power to the wheels independently; and mild hybrid vehicles, which use an electric motor primarily for acceleration assistance or regenerative braking. Hybrid cars are generally more fuel-efficient than traditional gasoline-powered vehicles due to their ability to recover energy during deceleration and reuse it later when needed.