What is a Ham Radio you might ask. Well Ham Radios are devices that are used to communicate with people from town to town or if what to go bigger the world. And the way they do this is through wavelengths. Plus the way they know how or what wavelength they are on deals with math.
How math work with ham radios is through MHz(Megahertz) and GHz(Gigahertz) to find your distance your wavelength is in meters. and centimeters.
For example if you are on a 2 m band you are using roughly about 30 to 300 MHz which is a VHF(Very High Frequency).
The way people know what their wavelength is through this formula:
λ(meters) = 300 divided by f(MHz) -- This is converting Frequency to Wavelengths
and
f(MHz) = 300 divided by λ(meters)-- This is converting Wavelengths to Frequency.
Ham devices differ in shapes and sizes as shown in this picture of someones ham radio station. Also ham radios can be be the size of a phone but with different features. But to use one you need a ham license.
Sources
This page by Elijah W. ('19)