[SickFinga]

Supercharger is belt driven - http://en.wikipedia.org/wiki/Supercharger
Turbocharger is exhaust driven. - http://en.wikipedia.org/wiki/Turbocharger


For E46 M3 your choices are.
Active Autowerke - http://aatuning.com
RMS - http://www.racemarque.com
ESS - http://www.esstuning.com
Dinan - http://www.dinanbmw.com/
VF-Engineering - http://www.vf-engineering.com/