Hi,
SVN:
Subversion (SVN) is a version control system initiated in 2000 by CollabNet Inc. It is used to maintain current and historical versions of files such as source code, web pages, and documentation. Its goal is to be a mostly-compatible successor to the widely used Concurrent Versions System (CVS).

Subversion is well-known in the open source community and is used on many open source projects, including Apache Software Foundation, KDE, Free Pascal, FreeBSD, GCC, Python, Django, Ruby, Mono, see more SourceForge.net, ExtJS and Tigris.org. Google Code also provides Subversion hosting for their open source projects. BountySource systems use it exclusively. Codeplex offers access to both Subversion as well as other types of clients.

Subversion is also being adopted in the corporate world. In a 2007 report by Forrester Research, Subversion was recognized as the sole leader in the Standalone Software Configuration Management (SCM) category and a strong performer in the Software Configuration and Change Management (SCCM) category.