Taken from Wikipedia:

VHF Stands for Very High Frequency

Its frequency range is from 30 MHz to 300 MHz. If you were able to see the radio wave with your eyes the 30 MHz wave would have a length of 10 meters peak to peak and the 300MHz frequency would have a wave length of 1 meter peak to peak.

VHF is commonly used for FM radio 88-108 MHZ and TV. Channel 2 is at 54 MHz and channel 13 is at 216 Mhz. They also use VHF for Aircraft navigation and communication systems.

Due to VHF's wave propagation characteristics it is ideal for short distance transmission. VHF is less affected by atmospheric noise than UHF. It also is less affected by buildings.

Under certain atmospheric conditions the VHF signal can reach much farther than usual. There have been rare cases where a TV station in Midland Texas was able to push Chicago's channel two off the air. These conditions may last for a few seconds or up to a few hours.

VHF was favored in the early days or TV and radio because it was easier to construct efficient transmitters, receivers, and antennas.

UHF Stands for Ultra High Frequency

Its frequency range is 300 MHz (Wavelength 1 meter) to  3.0 GHz (Wavelength 10 centimetres) . Anything beyond 3.0 GHz is considered microwave.

UHF is commonly used for Television transmission and Mobile Telephone communication.

Moisture in the air can degrade the UHF signal.

The ionosphere can also affect the the distance in which a UHF signal will travel. The signal will bounce off the ionosphere back down to the ground and then back up again. The temperature of the atmosphere will contribute to this affect.

The main advantage of UHF transmission is that because the wavelength is smaller, smaller transmitters and antenna can be used.