CVS
Short for Concurrent Version System, CVS is a software solution that helps keep track of all changes and versions of a software program. By using a CVS solution, a company can have several developers working on the same project without fear of overwriting each others work or losing any changes. CVS also has the ability to view and revert to older versions in case changes made caused conflicts.
CVS works by having a primary server or computer handle and keep track of all the changes made when clients commit their changes to the server. When a client submits its data to the server if no conflicts exist with the server version and the client version the two versions are merged. However, if conflicts exist before submitting the changes the CVS program displays the conflicts and enables the person to commit the changes or adjust their changes accordingly, so no additional conflicts occur after the merge.
There are several different CVS solutions available. One example of a free open-source CVS solutions is Subversion.
Also see: Compare, Diff, Programming definitions, RCS, Subversion