hi after a little info on how chips and boost works on a cossie

right lets say a standered cossie runnin standerd boost
then i put a stage 1 chip in it and the boost goes up and so does the bhp but is it the chip that makes it go up or does the chip just allow u to run more boost by adjustin the acurator
and same again for a stage 3 chip when this is fitted does it allow even more boost and fuel i no u need injector and a map sensor but just wondered how the chips work any lighht would be grate