Turbocharged engine is cheifly Power –boosted. Power is boosted by essentially burning more fuel and a bit more efficiently . This is done by packing more fuel in the same size chamber – you might have guessed this by now! Well the trick is to use a compressor for the air which is mixed with fuel –so more air and fuel can be mixed thus more energy(read power) is released. Dudes the compressor is a the turbine type(which is the most efficient type for practical purpose) hence the word Turbocharged .
I am gonna go fast on theory now… Now the turbine is generally driven from the exhaust as the pressure increases on high revs the turbo charging is more effective then.
Exited? there is more – Intercooler – if your vehicle is also intercooler turbo then additionally there are systems to cool the air intake and then compress air so that air is more efficiently compressed- remember gases compress on cooling.
Supercharging is a variant in which the compressor is coupled to the engine(mostly to the fly) – is preferred for certain designs, I guess mainly for petrol driven since the exhaust pressures are lesser and for operating over a wider rpm range the Benz Kompressor range are such examples.
Whatever the case extra power is achieved by burning more fuel and does not come free!, yes the engine is albeit more efficient at higher speeds .Retro fitting can be experimented by professional advice as it will affect other engine parameters mainly heat, engine and lube life. I have not covered details and the complete functions is not as easy as it seems.Hope you got the basics right and heres wishing you a happy ride .