After doing some browsing on my Mac, in the Utilities folder is an app called X11. I opened it, and it looked like terminal. Exactly what does X11 do... and How do I use it? Thanks!
I don't exactly understand it, but I know it helps various applications run in OS X. I know whenever I open Gimp (a image editing software) or Wine and WineBottler (apps to run Windows applications directly in OS X) it opens while I am using those applications.
*NIX applications are written to work with as many different systems as possible. One of the big issues with porting a *NIX application is the GUI since different targets use different GUI calls. X11 provides an interface between the *NIX applications and the GUI of the target system. X11 is a heavy duty protocol that provides a lot of flexibility.