Updates and release terminology

["Michael T. Davis" <DAVISM%ecr6.ohio-state.edu@localhost>]

        I've been reviewing the release glossary and graphs...

                http://www.netbsd.org/releases/release-map.html

...for several months.  I just can't seem to wrap my head around it.  The
graph is particularly confusing to me.  I suspect a good deal of my confusion
stems from what I believe is "overloading" of the term "release."  At any
rate, I think a concrete example of an update cycle would help me understand
things.  So, I have a system which is currently running "5.1 release."  I
believe this constitutes a "maintenance" or "stable" release, right?  I would
like to update to the "5.1.2 release," which I understand is a "security/
critical release."  What do I need to download to perform this update, and
what would be the process of maintaining things along these lines in the
future?

Thanks,
Mike