I have been researching about XQuartz a lot but I haven't been able to find much information.
I found out that it some kind of window manager provider.
I was wondering does it replace the default provider for Mavericks or does it run only for applications that need it?
Could I mess up the retina display?
I have installed it and removed it and my $DISPLAY variable is empty.
When I do echo $DISPLAY I get back an empty line, is this normal?
Best Answer
XQuartz is the continuation to Apple's deprecated X11.app which used to be part of OS X:
Source: About X11 for Mac - Apple Support
X11 is a very old windowing system for Unix that is not required for almost anything that you'll do on your Mac. The only widespread use of X11 that I use it for is Wine which allows you to run Windows software on your Mac.
XQuartz is very similar to X11, but is a 'community effort to further develop' X11:
XQuartz doesn't 'mess up' the Retina display. It doesn't replace any of OS X's window management. $DISPLAY is only used with and for XQuartz as far as I am aware.