It's called stroboscopic effect (at least I think you use the same term in English).
You get the same effect when looking at a spinning wheel and the lights going on and off very quickly (stroboscope). The eyes get confused and tell your brain that the wheel is standing still or even spinning in the opposite direction.
On cameras (digital or not) you get that effect when you set a high shutter speed.
Class dismiss ... lesson's over!