Linux has two ways of drawing pictures, the old way (Xorg) and the new way (Wayland).

The old way is like a giant box of crayons with the crayon sharpener built in. The box is all marked up, the sharpener is full of gunk, and a few crayons are melted together. Nobody really wants to touch the old box of crayons, although it does work for the most part, it's a familiar box.

The new way is like a smaller box of crayons. The clean sharpener isn't built in but it is available nearby, although some people say it doesn't work as good. A few crayons are missing, but are available in most cases, they're just not in the box. Most people are working to improve the new box.

If you're using Linux, the new box of crayons is generally the better choice. It's ok to stop using the old box.

You can check if you are using Xorg or Wayland in the Settings -> System -> About -> System Details page. If you're using Wayland, you're all good, nothing changes. If you're using Xorg, you may notice some changes. If you're using NVIDIA on Ubuntu 24.04, you'll be on Xorg by default. If you're using a later version or AMD/Intel, you'll be on Wayland be default.

To keep it short, X11 was the old protocol for creating and managing windows. Xorg implemented this protocol. But both the protocol and implementation have many shortcomings that are difficult to address for a multitude of reasons (breaking compatibility, poor code base, a ton of work, etc).

Rather than putting lipstick on a pig, a new protocol, called Wayland, was created. It was designed for modern needs and tries to avoid the pitfalls that X11, Windows, and MacOS have. It doesn't just copy what those three did, it's more opinionated, so some people love it a lot (like me) or hate it a lot because it changes the way things have to be done and simply does not implement some functionality, either purposefully or because the work hasn't been done yet.