I have read about servo motors but have problem grasping the main idea of obtaining fixed position by the magnetic field. The servo motor position is said to be controlled by PWM signal. And a toy DC motor speed can be controlled by PWM. I'm mostly wondering the electro-mechanical part rather than the feedback.
So in toy DC motor case the PWM controls the speed which I can make sense. But in servo motor case how come the PWM signal causes a non moving magnetic field? I guess servo motor works like a compass where the magnetic field is fixed(non-moving), is that correct? If so, is there a way to grasp the how the PWM causes such a magnetic field?