What is SVN (or subversion) ?

What Is Subversion? (please refer to http://svnbook.red-bean.com/en/1.6/svn.intro.whatis.html )

Subversion is a free/open source version control system (VCS). That is, Subversion manages files and directories, and the changes made to them, over time. This allows you to recover older versions of your data or examine the history of how your data changed. In this regard, many people think of a version control system as a sort of “time machine.”

 

How to use it ??? (please refer to http://svnbook.red-bean.com/en/1.7/svn.intro.quickstart.html )