What is the difference between a VHF handheld and a UHF handheld?

The terms "VHF" and "UHF" refer to parts of the radio spectrum. "VHF" refers to radio signals in the 30 Mhz to 300 Mhz range and includes many public safety and business communications systems; FM broadcasting, TV channels 2-13 and aviation radio. "UHF" refers to radio signals in the 300 Mhz to 3000 Mhz range. Until a decade or two ago, it was technically difficult or more expensive to build radios in this frequency range. As demand for radio usage has increased, the technology has improved and the costs of UHF radios have reduced so that VHF radio applications have moved or are moving to UHF. You will also find cellular phone service in this part of the radio spectrum; at the upper end you will find consumer microwave ovens and microwave "wireless cable" TV systems.