Superchargers

From wikipedia:

 A supercharger is an air compressor used for forced induction of an internal combustion engine. The greater mass flow-rate provides more oxygen to support combustion than would be available in a naturally-aspirated engine, which allows more fuel to be provided and more work to be done per cycle, increasing the power output of the engine.

A supercharger can be powered mechanically by a belt, gear, shaft, or chain connected to the engine's crankshaft. It can also be powered by an exhaust gas turbine. A turbine-driven supercharger is known as a turbocharger.

The key point is that fuel needs oxygen to burn.  More available oxygen = greater amounts of fuel that can be burned, which in turn = more power.

Many vehicles utilize superchargers to increase power.  Diesel engines, which typically are utilized to pull heavy loads, are generally turbocharged instead.  The exhaust gases produce the increased aspiration to the engine only when the pressure of the exhaust is above a certain point.  Thus, when the engine reaches a desired speed and the load drops off, the turbocharger spins down and ceases it's boost and fuel economy returns to normal.  Superchargers depend on the engine speed, rather than exhaust gas pressure, and thus continue to blaze through fuel at speed.  Only by slowing down do superchargers spin down and cease.

Here is a picture of a man with a beard of bees.  I have no idea why he'd want one.