These points are taken directly from the Subversion project web site.
Subversion is meant to be a better CVS, so it has most of CVS's features. Generally, Subversion's interface to a particular feature is similar to CVS's, except where there's a compelling reason to do otherwise.
Lack of these features is one of the most common complaints against CVS. Subversion versions not only file contents and file existence, but also directories, copies, and renames. It also allows arbitrary metadata ("properties") to be versioned along with any file or directory, and provides a mechanism for versioning the `execute' permission flag on files.
Do you need another version control system which is more scalable than Visual Source Safe? Are you a CVS user who finds the lack of directory versioning a difficulty? Are you paying too much for your current version control system? Do you not use a version control system right now?
If you answered yes to any of the above you need to look at the Subversion version control system.
The original design goal of Subversion was for it to be a compelling replacement for CVS. However, it is also an excellent version control system in its own right.