Warwick corvette $$ help with the knobs

Hi I recently purchased a used Warwick Corvette $$. It has three knobs and two of them can be pushed or pulled to get different sounds of the pickups. Here is my problem, I dont know exactly whats the difference between the knobs pushed or pulled, in the plastic thing that comes around the knob said something like "parallel" but I dont get what is that. This is my second bass, im a noob and english is not my first language so Im having a hard time understanding the technicalities