The literal translation of the term is a voltage reference. Stepper motors drivers have a device designed to maintain an accurate, low noise, constant output voltage. This is the exact description of what the driver does. The driver is the electronic device that takes care of guiding the stepper motor through the translation of the signals(an electric current) that are given to it by a processor.
Salmon skin is a recognizable print defect, for some, it is horrible to see, others find it characteristic. Despite all of this nobody wants it on their prints.