Homebrew (brew) is a package manager. It's designed to help you manage which apps you have install. As well as help you upgrade those apps or manage which versions you have installed. It's a command line app for Mac and Linux. It can install CLI apps and GUI apps.
It's difficult to explain homebrew well! It does many things. And uses strange terminology. Here is how I would explain brew. (Afterall, of the best ways to learn is to teach!)
https://formulae.brew.sh/ The official homebrew website for documentation on how to use brew.
You can use homebrew to manage the location(s) of where the apps are installed.