You are confusing a gas turbine engine with a turbocharger they operate on different principles.
The turbine section of a "jet" engine has stators and rotors, the stators expand the air and accelerate it focusing on the rotors. These are aerofoil shaped and act like a wing turning the shaft.
In the basic turbocharger gas pressure builds up against it and the act of the pressure flowing through the unit to the exhaust drives the shaft.