Delivery terminology and order of magnitude

Question

What is the standard way of describing how software products are released and the proportionate order of magnitude to which the changes relative to the software product are conveyed?

Is

1. Release
2. Update
3. Patch
4. Bug Fix

redundant?

or Is

1. Update
2. Patch

too terse?

As an end user I'd think that all bug fixes are patches (insofar as they are not 100% new code) and all patches should be updates (insofar as they don't degrade the product) and all updates should be releases (insofar as they are actually released), but this really doesn't help anyone understand why they need to get them.

Then, if the person who makes the software change appends "critical" or "zero-day" in the notes, I would be unwise to leave the changes unapplied.