How Linux’s insanely customizable desktop works
Quoting: How Linux's insanely customizable desktop works | PCWorld —
Among Linux desktops, the X server Xorg still generally works as a display server. The X server is the hardware-related basis of the graphical user interface.
All the components mentioned below are clients that depend on the X server. Xorg is pre-installed on every Linux desktop and runs as standard. Only on pure server systems without an interface (e.g. the Ubuntu server) is Xorg consistently missing, as are all downstream desktop components.
Wayland is still an experimental replacement for the old Xorg in some desktop distributions, optionally in Ubuntu Gnome and already as standard in Fedora. Wayland has a significant, simplifying advantage over the old X server. It combines the functions of the display server (point 1) and the window manager (point 3), including the compositor.