The document compares turbochargers and superchargers. It states that turbochargers are driven by exhaust gases and are more efficient, but take time to reach operating speed after throttle opening. Superchargers are driven mechanically by the engine and are less efficient, but provide an instantaneous power increase. The key difference is that turbochargers are powered by exhaust gas turbine, while superchargers are mechanically driven, often by a belt connected to the crankshaft.