X.org

X.org, also known as X11 or sometimes simply X, is the default windowing system in Ultima Linux. To grossly oversimplify, X runs between the kernel and applications such as Firefox, OpenOffice.org, or KDE, so that they can access the system's video card, keyboard/mouse, etc. without having to know how to directly access them.

X11 is the main feature of Ultima Linux's X series.