Turbocharger is a supercharger powered by an exhaust gas turbine. Turbochargers are commonly known as a turbo.
Turbochargers were originally known as turbosuperchargers when all forced induction devices were classified as superchargers. Nowadays the term "supercharger" is usually applied only to mechanically driven forced induction devices. The key difference between a turbocharger and a conventional supercharger is that a supercharger is mechanically driven by the engine, often through a belt connected to the crankshaft, whereas a turbocharger is powered by a turbine driven by the engine's exhaust gas. Compared to a mechanically driven supercharger, turbochargers tend to be more efficient, but less responsive.
Turbochargers are composed of two main parts: a turbine and a compressor. The turbine uses engine exhaust to spin an impeller. The turbine impeller is connected to and drives the compressor. The compressor acts like a fan that compresses air and forces it into the engine. The compressed air is more dense and contains more oxygen. This added oxygen allows more fuel to burn which produces more power.
Turbocharging can dramatically improve an engine's specific power and power-to-weight ratio, performance characteristics that are normally poor in non-turbocharged Diesel engines. Diesel engines have no detonation because Diesel fuel is injected at or towards the end of the compression stroke and is ignited solely by the heat of compression of the charge air. Because of this, Diesel engines can use a much higher boost pressure than spark ignition engines, limited only by the engine's ability to withstand the additional heat and pressure.