Answer:
It depends on the "handedness" of the thread of the screw. Most screws have right-handed threads that in order to loosen the screw, the screw is turned in a counterclockwise direction. If however, the screw has a left-handed thread, then to loosen it you would turn the screw in a clockwise direction. By common convention, right-handedness is the default handedness for screw threads. Therefore, most threaded parts and fasteners have right-handed threads so to loosen most screws you would turn the screw in a counterclockwise direction.