The intake of an engine has a friction. This makes that the
volume of air taken in to the engines, for each turn, gets lower when the speed
of the engine increases. So does the energy delivered bij each turn.
The solution is to pump more air in to the engine when the engine speed is
This pump is called "super charger"
The energy for the super charger can be supplied by an electric engine or by a
turbine mounted in the exhaust. When the energy comes from a turbine in the
exhaust we call it a turbo charger.