[Shywim]

In short: X.org is a decade old display server that became the standard to display graphical window on the majority of Linux distribution. GNOME, KDE, XFCE and others are/were client to this display server.

Wayland is a new protocol where the window manager (ie GNOME, KDE,...) is responsible of directly managing the display. Each window manager must reimplement this protocol (or use a library already doing this work) which enable them to have more control over the windows.

Applications must also directly support Wayland like they did for X.org before (which was the default commonly used, so no problem) or the user just have XWayland installed on their computer to show X.org windows inside a Wayland WM but then the application may not display correctly (blur, artifcats,...)

[ch_123]

It is perhaps worth noting that while X.org is about a decade old, it is an implementation of the X Window System protocol which dates back to the mid 80s.

Suffice to say, quite a lot has changed in computer graphics/interfaces since that time, and most modern *nix operating systems end up circumventing quite a lot of X to offer modern features. Thus X brings quite a lot of legacy debt to the table which can't be easily removed.

[oblio]

Also, even back in the day, X wasn't considered the best tech around, at least by some. For example: https://en.wikipedia.org/wiki/NeWS was around.

However NeWS' licensing was proprietary and X won out.

[unstuckdev]

Gopher and HTTP had a similar situation. Gopher had a lot going for it, but the future licensing situation was unclear. HTTP was free, clear, and widespread by the time Gopher became GPL.