Spanner Turner has it mostly right - but wait, there's more!
The compressor (& fan) rotor blades impart the energy to the air, but it exists in the form of a helical or vortex flow. In other words it's not flowing straight aft, but is rotating in the direction the rotor throws it.
SO - behind each rotor stage there is a stator stage. The stator vanes (think of venetian blinds) straighten the airflow to a straight-aft direction. In so doing, they recover some static pressure (they behave like a diffuser), and there is a fair amount of additional thrust recovered (from the lift vector of the stator airfoil).
The rotor won't work right without the stator.
