Any system that pushes more air into the engine than it could draw in by itself — turbocharging or supercharging. More air means more fuel can be burned, so more power from the same displacement.
Forced induction
Engine
in short
Engine
Any system that pushes more air into the engine than it could draw in by itself — turbocharging or supercharging. More air means more fuel can be burned, so more power from the same displacement.