for hybrid vehicles that can be plugged-in to recharge their batteries. These usually have a longer electric range than regular hybrids which allows them to take short trips on electricity only.

Regenerative braking is a feature in hybrid cars that allows the motor to act as a generator when braking. The process converts kinetic energy of the car's motion into electric energy that recharges the battery.

Type I hybrids are a definition by the California Air Resources Board, and the term was actually originally conceived as an industry-standard improvement to the 12-volt systems in all conventional cars (to 42-volt systems). Type I vehicles can only be called hybrids if they provide traction power to the wheels, offer regenerative braking and have an idle-stop feature that turns engine off at a stop.

Also known as an "assist" or "mild" hybrid. Type II hybrid car is a definition by the California Air Resources Board for hybrids that typically have a smaller traction battery and motor, and provide peak power for the engine during acceleration. However, Type II hybrids currently in production do not allow electric-only driving.

Also known as "full" hybrids. Type III hybrids are a definition by the California Air Resources Board for hybrid cars that can operate in electric-only mode during low-power driving.

adjusts the operation of an engine’s valves depending on engine speed and power demand. By providing a better fuel/air mix and improved combustion, these technologies boost fuel efficiency.