There is a large amount of detailed information available about the X server, the clients that connect to it, and the assorted desktop environments and window managers.
7.6.1. Installed Documentation
/usr/X11R6/lib/X11/doc/README — Briefly describes the XFree86 architecture and how to get additional information about the XFree86 project as a new user.
/usr/X11R6/lib/X11/doc/RELNOTES — For advanced users that want to read about the latest features available in XFree86.
man xorg.conf — Contains information about the
xorg.conf configuration files, including the meaning and syntax for the different sections within the files.
man X.Org — The primary man page for X.Org Foundation information.
man Xorg — Describes the X11R6.8 display server.