On Linux, as on all other Unix-like OS, windowed sub-system with messaging is based on X Window:
http://en.wikipedia.org/wiki/X_Window_System[
^].
Now, a particular system may of may not include X Window System, as well as other sub-systems based on it. Unix and Linux is not anything fixed. Also, a particular Linux distro also is not the indication of any particular windowed sub-system configuration, which may vary; for example, Ubuntu server does not have it, and there are variations of desktop Ubuntu preferring different
desktop enviromnents; even if some distro is already installed, the desktop environment can be later replaced.
A particular system is the superposition of a number of optional components, such as X-Window, a desktop environment on top of that, such as GNOME, KDE or Unity. Please see:
http://en.wikipedia.org/wiki/Desktop_environment[
^].
These layers do not belong to any particular Linux distro but are shared by many of them. At the same time, different distro provide different sets of those layers and typically offer the optional sets of features.
—SA