The difference between UHF, ultra-high frequency, and VHF, very high frequency, is that the frequencies used in UHF are much higher than those in VHF. Both, however, are relatively high frequencies for radio waves as the names imply. Signals sent via VHF are less directional and travel further than UHF signals, making them preferable for their typical purpose of broadcasting television.
Both UHF and VHF broadcasting are declining in use as television is increasingly received through cable and satellite services; however, several channels in each are still designated by the government for use. While VHF signals have a greater range and ability to broadcast through or around physical obstacles, UHF signals are more resistant to common types of electromagnetic interference.
Receivers and transmitters of UHF signals tend to be more expensive than those for VHF receivers, as dealing with the higher frequencies requires more specialized equipment. UHF antennas are often more compact than VHF antennas, making them preferable in some situations. Because of their reduced range, UHF systems often require substantially more power to work properly.
While UHF has many disadvantages, it is often preferable when transmitting from an urban environment. These environments have an abundance of electromagnetic interference sources that are minimized with UHF signals.