There are 3 types of frequency used (or about to be used) for the delivery of 5G in the UK - low, mid and high bands. Each has their own characteristics defined by the basic equation from physics:

c = f λ
(speed of light) = (frequency) * (wavelength)

This means that the higher the frequency the shorter the wavelength. A shorter wavelength will travel a shorter distance will not penetrate buildings, but on the other hand the associated higher frequency can deliver more data capacity. Thus the frequencies are used for different purposes

Low Band Waves: which in 5G terms is the 700MHz waves. These waves are used to provide coverage over large geographic areas with a coverage of around 3.5km for each mast. They have similar qualities to the 800MHz or 900MHz waves used in 4G and 2G networks. These waves provide a background coverage but this is neither fast nor the capacity to deliver the 5G demand in highly populated areas.

Mid Band Waves : these are designed to add capacity in our towns and cities where there is heave demand. In 5G the frequencies are in the 3.4GHz to 3.8GHz range. Typically these waves will be able to travel up to 1km but deliver 5 times the capacity of the low band waves.

High Band Waves : [In the UK licenses for these waves have not yet been released]. These are the so called mmWaves in the 26GHz range. The downside of these waves is that they will only be able to travel 100m-200m but the capacity will be 15-30 times that of the low band waves. This leads to these waves being used for very specific applications. They will be used in Sports arenas, shopping malls etc where there is a very high capacity, as well as in novel applications in these areas, they will also be used in industrial applications.