What follows are command specifically pertaining to X11.
X
X is normally a symbolic link to the X server for your computer, such as XFree86 or Xorg. The normal way to start X is not directly, but by using xinit , xdm or startx.
You can invoke the X server with
$ X -quiet -query remotemachineaddress
to get a graphical login screen for the remote machine. See xdm.
xbiff
xbiff displays a small box indicating whether your local Unix inbox has mail. Start with:
$ xbiff
xcalc
xcalc draws a window with a scientific calculator. The easiest way to operate the calculator is to click the buttons. The calculator understands order of operations (multiply before add) and provides common functions such as sine, square root, and the values of e and pi. The calculator normally displays eight digits and supports scientific notation.
xclipboard
Xconfigurator
xdm
An X display manager used to manage graphical sessions of multiple users. It is usually started automatically as a system service to present the user with a GUI login screen instead of the console login prompt. Modern systems usually use GDM (the GNOME Display Manager) and KDM (the KDE Display Manager) instead.
xdvi
A normal program not a part of X11 itself, for viewing DVI form
at typesetting graphics files, *not* related to the Digital Visual Interface video port (which *is* important to X11 itself). :)