Before working on files in your local working copy, and from time to time during your work, you need to update your copy with changes that others have made to the repository.
$ cvs update cvs update: Updating . U Makefile M hello.py $
Here Makefile has been updated with changes and hello.py has been modified locally (i.e. there are changes in the local working copy that have not yet been committed to the repository.
However, regular cvs update does not include new directories, nor does it remove files that are no longer needed. Need to supply -d to add directories and -P to "prune" files that are no longer necessary, as in the example:
$ cvs update -dP