CSS *vh (dvh, lvh, svh) and *vw units
This background section is large; here's a handy link to the new unit section if you would like to skip ahead. However, I think it can be useful to understand how we got where we are. Additionally, this information will be useful to understand when talking about the dvh and dvw units later.
https://dev.to/frehner/css-vh-dvh-lvh-svh-and-vw-units-27k4