Subversion (or SVN) is a version-control system, i.e. it helps you to keep track of a filesystem as you make changes, recover older versions of files, and compare different versions. This site acts as a Subversion server, allowing users to share a filesystem concurrently. Here are some background links:
The project's original goal of beinga compelling replacement for CVS(an older version control system with a similar model), was surpassed long ago — today Subversion stands on its own highly reputable name.
This site provides the bulk of the Subversion software and documentation. It also points to other related software.
This is the free on-line book (in English, Spanish, Italian, Japanese, Norwegian Bokmål, Brazilian Portugese, Russian and Chinese) about how to use Subversion.
The new and old archives of the Subversion Users' mailing list
A comparison of over a dozen version-control systems