A "hybrid" is a vehicle that has both an internal combustion engine and one or more electric motors that operate (in unison and/or independently) to propel the vehicle. An onboard battery pack supplies power to the electric motors. Typically, the electric motors also function as generators, recapturing kinetic energy when the vehicle is coasting and braking to recharge the battery pack.

Additionally, there are some “hybrid” vehicles that are solely propelled by an internal combustion engine with a fuel shutoff mechanism that triggers when the vehicle is slowing down and/or stopped. These vehicles also have an electric motor that serves as both the vehicle’s alternator (allowing it to restart the engine when pulling away from a stop), as well as an onboard generator (allowing it to supply power to auxiliary equipment).