Well if you want to get technical, Nos just adds extra Oxygen to the fuel mixture making it more reactive and giving you more power. So in fact it does excellerate ignition (burn). It just won't do anything by itself.
Why would you put anything that doesn't burn in the engine? Actually you can put water in it. In WW2 various aircraft engines had a water injection system that added spurts of water during points of the four stroke cycle, therefore cooling the cylinders a bit and giving more power. It wasn't just water though; a combo of water and methyl alcohol was used.
A supercharger is a device used in piston engined aircraft. It's basically a compressor driven by either the engine or exhaust gasses to compress intake air in order to compensate for the loss of oxygen at altitude. A turbocharger works the same but is generally used in cars.
I'm sure you all feel extremely enlightened.
