VP and Constant Speed
I may be wrong, but as a simplifiedanswer, I believe that a VP prop can have its pitch varied by the pilot to a pitch angle that they hope suits the airframe speed, but no more. For instance, a fine pitch can be selected for take-off and a coarse pitch for the cruise. A constant speed prop has the addition of a governor that maintains a constant engine rpm, regardless of throttle position. There are limits, of course, depending on the handling of the aircraft