Both are used to increase the volumetric efficiency of an engine by the method of forced induction. The method is based on the principle that an engine will produce more power at the same speed if more air-fuel mixture is forced into it.. This means higher pressure during power stroke and higher power output.
Superchargers and Turbochargers are two pumps or blowers that force more air-fuel mixture in the cylinder. They both differ in construction and operation but the basic difference:
Supercharger: This is mechanically driven by belt/chain from engine crankshaft. Noisy and poor economy. Was used extensively earlier. Does not have problem of turbo lag therefore is still used for some high performance engines. Instant response when accelerator is pressed. Unlike turbocharger, does not turn at high speeds. New designs have improved economy and lessened noise.
Turbocharger: A centrifugal pump driven by the engine exhaust gases. Prone to detonation because of higher peak cylinder pressure, therefore compression ratios have to be reduced, this results in lower air standard efficiency. Limited use in Petrol Engine but is extensively used in Diesel Engine because - increase in power output, better torque characteristics, more B.P/weight ratio, power loss due to decrease in air density at higher altitudes reduced, reduced gas emission.