UHF and VHF (that is, Ultra High Frequency and Very High Frequency) are the 3GHz-300MHz range and the 300MHz-30MHz range, respectively.
That translates to a 10cm-1m wavelength for UHF and 1m-10m for VHF. Minimal effective antenna size for a basic wire antenna is 1/4 the wavelength, so you end up with big antennas for low frequency / large wavelength.