Hertz = cycles per second. So as far as any sort of display (TV, monitor, phone, gameboy) has a frequency, rated as hertz, which it refreshes itself, per second.
So your TV is 60Hz refresh rate. If your GPU is pushing out 75fps, those extra 15 frames will not be displayed as your TV will only refresh itself to a maximum of 60 times per second(60Hz), therefore dropping excess frames being sent to it from the GPU.
When you have this kind of fps overhead, it's (imo) best to enable vertical sync which will make it far more smooth than viewing 100+fps @ 60Hz. And virtually will eliminate screen tearing.
FPS in excess of 60 will not do anything to harm your TV.