This guide is merely an introduction and basic install guide to the Subversion system, which is useful for setting up – and, particularly, for keeping up-to-date – archives and software packages.
Subversion can be used to download and help administer many many platforms, architechtures, scripts and so on so, if your sites rely on regularly updating code, check to see if that's looked after on Subversion's repository.
So, as I say, if you have a popular platform (part-)powering your site such as Simple Machines Forum, Drupal, WordPress and much more besides, Subversion is a handy tool.
So what is Subversion?
To recap, Subversion is a version control system. Basically, and easily, it keeps key platforms up-to-date, at the issue of a simple command. I use it to upgrade not only WordPress, but also all of my plugins. It simplifies the initial WordPress installation immensely.
Install by typing:-
.. simple as that.
To get an idea of how to use it, read WordPress Setup & Updates from the Command Line, which illustrates the basic Subversion commands.