The Shifter section provides control over the direction of frequency shift, and feedback of the signal through the algorithm.
Shifts frequencies equally up and down, and the two shifted signals are heard simultaneously.
The Feedback control lets you run the signal through the pitch shifting algorithm multiple times, creating a cascading, layered effect.
The Mix control lets you balance the amount of dry signal with the amount of wet (pitch-shifted) signal. At 50%, there are equal amounts of dry and wet signal. At 0%, the output is all dry and at 100% it is all wet.