Here's the basic rundown: Most if not all desktop environments for Linux have used a component called X11, which is the window manager. X11 is exceptionally old; it's been around since the 1980's. Computer display technology - and what we expect computer displays to do - has changed drastically since X11's creation. X11 is old and busted, there's stuff it just outright can't do that we're beginning to expect computers to do. But, because it has been around for so long, a lot of software is written with X11 in mind, sometimes software that isn't actively developed anymore.

If X11 is old and busted, Wayland is the new hotness. Wayland has been in development for approximately ten years now; when I started getting into Linux in early 2014 I heard whispers that there were a couple projects working to replace X11, Canonical was working on their thing, Mir, and there's this other thing called Wayland.

Wayland is actually out and in service, and it can do some cool things, but also it breaks a lot of things, especially for users of Nvidia GPUs if my understanding is correct. We're still not at a point where we can kick X11 in the head and standardize the whole Linux world on Wayland yet.

Cinnamon - Mint's signature DE - hasn't even begun to try to switch over to Wayland. I'm a Cinnamon user, I'm extremely still using X11, I don't even know if I've ever run Wayland on my current hardware, so I don't have much practical experience with it.