Since the other replies don’t seem too beginner friendly I’ll try another way:

The desktop environment determines how your taskbar looks and your start menu. Also the edges windows and the buttons to close and minimize windows. Also some basic programs like the system settings.

Mint and bazzite are distributions. They bundle software, test it and sometimes develop it further (like the mint guys do with their desktop environment cinnamon). Also they provide the package manager and the packages and their versions that can be installed through it. (Others can always be installed through other means but a lot is available through it)

I want to add, that especially for Germans (and maybe others) the Usenet is very much full of up-to-date media and software.