Superchargers work by compressing air to above atmospheric pressures and pushing it into the engine. Compressing the air means there is higher rate of oxygen flowing into the engine, allowing for more fuel to be added and combusted for more power.
Superchargers are driven by the mechanical power of the engine by use of a pulley that is attached to the crankshaft with a drive belt. This is unlike turbochargers, which use the exhaust gas of the engine to drive the compressor. Because superchargers must spin very fast in order to compress the air, the drive gear attached to the pulley is made much larger than the gear that drives the compressor. This means that while the engine spins at a maximum of 7,000 RPM, the compressor spins as high as 50,000 to 65,000 rpm.
Air gets hot as it is compressed, which is not desirable because hot air is less dense than colder air and therefore contains less oxygen. The air that is compressed from the supercharger is typically passed through an intercooler to combat this problem. The intercooler exchanges the heat from the hot air for cooler air that is passing through the intercooler or the water flowing through it.