Frequency is measured in hertz. If you know the energy level and wavelength of something, you can find the frequency. All radio signals, and lights and sound travel at different frequencies on wavelengths. It's like when you press a button on your tv, and it turns to static. The number of hertz is how you measure the frequency that your tv is able to time into a signal (and display tv shows). Got that from chemistry class.
Lower hertz will give stop gaps in motion, higher hertz will give seamless motion. Like the Mac-cam in tennis that takes something like 1000 frames per second to see whether the ball was inbounds or not.
In transmitting a signal, such as your television picks up, there is an amplification, or boost, that the radio waves, are initially given. The term for the measurement of those waves is hertz. As far as in relation to you tv, assuming it's not broadcasting anything, I'd suppose it refers to its reception capacity. Hope I helped!