You mean if you point a camera at a TV? The camera and TV do their thing in different ways - the camera takes full images 30 times a second, while the tv scans the frame one line at a time, 60 times a second. As a result, the camera sees the scanning of the tv.
Same effect can be demonstrated when watching a spinning wheel or a car tire. Our brain/eyes have some specific sampling frequency at which they "sample" the outside world. When the frequency of angular rotation is slightly higher then the sampling speed (angular speed < sampling speed < 2*angular speed) you're getting an effect which is called " folding" (sampled frequency is switched with a complex conjugate variant of itself + phase shift) and this effect causes you to see the wheel spin the other way. ;) Quite interesting actually, since it can be applied everywhere. Such as filming a computer screen or watching a movie etc..
I don't think that the so-called strobe effect happens in the 'REAL' real world. What I mean by this is that it is not noticed in good old plain and pure sunlight. It is noticed under artificial lighting due to the 50/60 hertz that our eyes cannot see normally.