cvs rtag vs cvs tag

[Matthew Berney]

Currently we do development on a branch and then merge individual changes
onto the branch.  We use a branch tag, lets call "codeline-branch".  Each
night, we perform a build and then tag the build with a static tag:
"codeline-static-DATE".

What is the difference between cvs rtag and cvs tag?  Should we be using
rtag in this case?  Under what circumstances do you use rtag instead of tag?

Thanks,

Matt