Superchargers are a form of forced induction which uses rotational energy from the engine to force air into the intake. This improves power and torque, and doesn't use exhaust gasses like a turbocharger does, and doesn't require the vehicle to be moving at high speed like ram air does. The three main types are twin-screw superchargers, centrifugal superchargers, and roots superchargers. Each of them has more parasitic drag (power lost in order to power them) than a turbocharger, but generally produce less heat.
These superchargers have two screw-like components that compress air as it progresses through the supercharger chamber. They look similar to roots superchargers both inside and out, but the design of the roots type compresses air in the intake manifold instead of under its own force. This supercharger makes a lot of low to middle RPM range torque and generates relatively little heat, but is relatively expensive (because the screws need custom precision engineering). Because of its design, it has to be positioned after (in regards to the air flow in the intake towards the engine) the throttle body, which makes controlling the idle RPM difficult.
These superchargers most resemble turbochargers. It uses cetrifugal forces generated by a high-speed propeller to draw air into the center, and outwards, where the opening leading to the rest of the intake is. Unlike its twin-screw and roots counterparts, centrifugal superchargers require engine oil to work. This type also generates more heat than the other two designs and most of the torque gains are in the high end of the RPM range. The main advantage to this design is that it is small and can be located before the throttle body.