Definition of Boost
Before learn what is boost we need to define which boost we are actually referring to. We are not improving moral, productivity or stealing something. We are talking about boosting an engine via a supercharger or turbocharger. In the simplest form an engine is an air compressor. It sucks atmospheric air in, then a piston travels up and compresses the air. Fuel and fire is added and you have an explosion. The keyword I specified here is atmospheric air. At sea level there is approximately 14.7 PSI that helps push the air into the vacuum of the engine. At higher elevations like Denver atmospheric pressure may be around 12.1PSI which is why engines are less powerful in the higher elevations.
What if I told you would could run in a magical made up place where the atmospheric pressure is 29.4PSI. Can you imagine how much air would be sucked into the engine then? In an ideal scenario it would suck in twice as many air molecules. This means I can add twice as much fuel and have twice as big of an explosion. This is essentially boosting an engine. Trying to figure out how to get more air into the engine. This can be accomplished via turbo chargers, Superchargers, and Nitrous oxide.