CVS stands for Concurrent Versions System, and is a version control system, where different versions of a file will be stored. First and foremost, you have to install CVS on the server that will be using CVS.
Check Out / Add / Update / Remove
The general flow of working with files in CVS is to first do a check out, which refreshes your CVS repository so that you are working with the latest version of each file in CVS. Then, you can add, update or remove a file in CVS.
Status / Log / Differences
When first learning CVS, or when debugging some issue with a file, you'll almost always want to view the status of the file and view the log, which lists what was done to the file at each revision. You may also want to list the differences between the file at certain revisions.
Restoring a prior revision
One of the less obvious tasks is to revert to a prior revision of a file.