Desktop Environment
The desktop environment is the interface of your system. Think of the differences between Windows 7, Vista, 8, 10, 11. That's the Desktop Environment (DE). The good thing on Linux is, that you have large choice about what to use. And you can even install multiple DEs at the same time and switch between them!
The most popular options are the following:
Gnome
The default on Pop!_OS. Polished, easy to use, but customizing is a bit tricky. If you don't want to mess with it too much, it's a solid choice. It supports display unredirection, so you don't even have to mess with composition (but you do loose a little bit of responsiveness).
KDE
Looks much like Windows, and has many nice quality of life features. Easy to customize, but if you're not careful you might break it. Supports disabling composition.
Xfce
Cinnamon
People often seem to report problems. Disabling composition might be problematic.