A turbocharger or colloquially turbocharged is a forced turbine driven induction device that increases the efficiency of the internal combustion engine and the output power by forcing extra air into the combustion chamber. This improvement over the power output of a naturally aspirated engine is due to the fact that the compressor can force more air - and proportionally more fuel - into the combustion chamber than atmospheric pressure (and, in this case, of air).
Turbochargers were originally known as turbo-superchargers when all forced induction devices were classified as superchargers. Today, the term "compressor" is normally applied only to mechanically driven forced induction devices. The key difference between a turbocharger and a conventional supercharger is that a compressor is driven mechanically by the engine, often through a belt connected to the crankshaft, while a turbocharger is driven by a turbine driven by the engine exhaust. Compared to a mechanically driven supercharger, turbochargers tend to be more efficient, but less sensitive. Twin-charger refers to a motor with a supercharger and a turbocharger.
Turbochargers are commonly used in trucks, cars, trains, aircraft and construction equipment engines. They are most often used with Otto and Diesel cycle engines. They have also been found useful in automotive fuel cells.