Electromagnetic radiation/frequencies (EMF) are waves of energy that travel at the speed of light, and carry information which is used in nature and by electronics to communicate.
EMF is classified by wavelength. Taller waves like from Wifi have lower frequencies and lesser intensity, while shorter waves like from 5G cell phones have higher frequencies and more intensity.
Some EMF like from the sun can be beneficial to our bodies, but too much exposure can be harmful.
The proliferation of wireless technologies, like smart homes and the internet of things, are exposing us to unprecedented levels of unnatural EMF.