doc/tag: candidate explanation of tag workflow

Some suggestions re: tag workflow.  Open to major revision/bikeshedding.

There is a distinction between 'tag' (eg a git tag) which identifies a specific release (and is very closely related to 'version') and 'dist-tag' which identifies both a stream of releases and the most current version in that release, but I am having a hard time articulating it.

Is the name "tag" or "dist-tag" still open to bikeshedding or is it basically set in stone?