A content management system with version control assists the users of the system in coordinating production & tracking older versions of content or code. It can provide the following benefits:

Coordination: making sure, by default, that only one person at a time is modifying a file. This prevents files from accidentally being replaced by another user's changes. This is typically done by requiring users to "check in" and "check out" files that they are working on, as they would books in a public library.
Branching/Reconciliation: This functionality allows multiple simultaneous revisions to a file, and the changes will be reconciled before the file is published to the live site. A system with this feature allows multiple checkouts of a file by different people.
Version tracking: archiving and tracking old versions of content, the content management system's source code, and other files, which can be retrieved and re-published to the live site. This is done using time and date stamping, and other data about a file to maintain it.