Very High Frequency, also described as FM, Frequency Modulated. There are three basic ways of sending information over the air waves. CW, Carrier Wave. This is an un modulated sine wave, which is switched in or off, such as Morse. The result is a buzz. The beauty of this system is the waveform can be very simple, so can the equipment as the only information sent is the carrier is either on or off. It is also suitable for all wavelenghths.
Long wave /Medium Wave. These are also called AM Amplitude Modulation. In this the Amplitude or height of the sine wave is varied. It was the first succesful system to transmit spech. The drawback is you need large sine waves in order to modulate enough to get all the information through.
VHF Very high Frequency. The frequency , or number of time the sine wave is sent is used to transmit information. This requires the speed of production of sine wave to be high. As the speed of the prodution is the frquency, think of a musical note, you get Very High Frequency. The beauty of this system is that it can switched very fast, and allowed stereo brodcasting . Problem is it is limited in range, basically line of sight. You can send a weak VHF signal to the moon, but it wont go to the next street.
All this is a very basic explination, and now Phase modulation is being introduced, but please don't ask for an explanation of that! I'm trying to understnd it, but all I have so far is a headache. :-D