to see the listing of all available command (on your PATH). On my small
home system, it says there are 2595 executables on my PATH. Many
of these "commands" can be accessed from your favourite GUI front-end (probably
KDE or Gnome) by clicking on the right menu or button. They can all be
run from the command line. Programs that require GUI have to be run
from a terminal opened under a GUI.

