X11 is the X Window system. It’s a graphical user interface employed by some Unix applications, and it’s included as part of Mac OS X v10.4 “Tiger.” It enables Mac OS X to run Unix applications that aren’t designed to use Mac OS X’s graphics technology specifically; it includes a server, window manager, libraries and basic components that X11-compatible Unix applications need to function.
The earlier update had been released to address problems with GLX stereo visuals — some X11 applications can be used for 3D visualization, and GLX stereo imagery makes it possible to actually view those 3D images using 3D optical displays.
This release “also addresses font issues present in X11 1.1.2,” according to Apple, which recommends it for all users.
System requirements call for Mac OS X v10.4.8 or later and X11 1.1 or later.
This story, "Apple's X11 fixes font problems" was originally published by PCWorld.