Original and genuinely made to force more air into the engine’s cylinders so it can burn more fuel and make more power.
It uses exhaust gases that would normally be wasted to spin a turbine, which drives a compressor. The compressor pushes extra air into the intake at higher pressure than normal atmospheric air. More air means more oxygen for combustion, so the engine produces more horsepower and torque without needing a bigger displacement.
It also improves engine efficiency because it recovers energy from the exhaust to help the engine breathe better.