in real lamens non technical terms a turbo'd car runs boost.

this is measured as boost pressure which can be measured as units of PSI or BAR (exactly the same pressure units you use when you pump up your tyres)

The amount of boost pressure your car runs will be pre set at factory.

Its a misconception that the higher the boost pressue the faster the car. Its not quite as simple as that but with the correct modifications elsewhere (fueling etc) an increase in boost pressure is a great way to make a turbo'd car faster.