Rick, don't consider me a git expert by any means. My understanding of git is that it is a program created by the creator of Linux. The purpose is to make it possible for hundreds of different people to work on all the various pieces and parts of a huge piece of software. GIT keeps track of everything somehow and makes everything nice or happy or something.
I am going to go out on a limb and suppose that the moodle development community uses GIT to organize the work on all the various branches of the software.
This being the case, just one or two simple commands is all it takes to sync your installation up with the most up to date and stable version of moodle.
What I don't know is if it allows a simple jump from moodle 2.2 to 2.3 or from 2.3 to 2.4 or whatever.
I am sure that it is the easiest way to keep your version 2.2 up to date with all the latest fixes or 2.3 up to date with all those latest fixes.
I hope this helps.