A turbocharger, or turbo is a turbine driven forced induction device used to allow more power to be produced by an engine of a given size. A turbocharged engine can be more powerful and efficient than a naturally aspirated engine because the turbine forces more air, and proportionately more fuel, into the combustion chamber than atmospheric pressure alone.
Turbochargers were originally known as turbosuperchargers when all forced induction devices were classified as superchargers; nowadays the term "supercharger" is usually applied to only mechanically driven forced induction devices. The key difference between a turbocharger and a conventional supercharger is that the latter is mechanically driven from the engine, often from a belt connected to the crankshaft, whereas a turbocharger is powered by a turbine that is driven by the engine's exhaust gas. Compared to a mechanically-driven supercharger, turbochargers tend to be more efficient but less responsive. Twincharger refers to an engine which has both a supercharger and a turbocharger.