A supercharger is an air compressor used for forced induction of an internal combustion engine.
The greater mass flow-rate provides more oxygen to support combustion than would be available in a naturally aspirated engine, which allows more fuel to be burned and more work to be done per cycle, increasing the power output of the engine.
Power for the unit can come mechanically by a belt, gear, shaft, or chain connected to the engine's crankshaft.
When power comes from an exhaust gas turbine a supercharger is known as a turbosupercharger – typically referred to simply as a turbocharger or just turbo. Common usage restricts the term supercharger to mechanically driven units.
Read more about Supercharger: History, Types of Supercharger, Two-stroke Engines, Automobiles