you have an intake side turbine, and an exhaust side turbine, the exhasut side spins the as the motors exhaust is pushed throught he pipes, the intake side is therefore spinning at the same time(however at a different trim) and forcing air into the motor. Thus creates boost in the intake track, that increases with rpm.
i am not good at explaining things so someone will prob. have to hel pbut thats a start
Think of 2 windmills facing each other with a spindle connect them at the center. If the wind blows on one of them (exhaust side from the exhaust flow) , they will both spin, and the one that is being spun is creating its own air flow (intake side)
Thats why Turbos are called "scavengers", because they use "waste" exhaust fumes to create power.
A supercharger is a belt driven pump that forces the air into the intake.
A turbo is the same thing more or less except instead of being driven by a belt the shaft (that would have the pulley on it) has another turbine on it and your exhaust leaves your headers and enters this turbine turning its shaft and that shaft turns the airpump (like a supercharger)