For the sake of those who can't be bothered to follow the link (and a very good one it is too)...
A supercharger uses some of the driving force produced by the engine to compress the fuel-air mixture as it enters the cylinders - thereby increasing the content of fuel/air for the same sized cylinder and increasing power output.
A turbocharger works the same way but used the exhaust gas pressure to drive the unit that does the compressing as opposed to using the driving force of the engine - it is a less efficient and less responsive but cheaper alternative to supercharging.