<hgroup>
A heading and its subtitle tied into a single block.
After some back and forth in the specification, <hgroup> now accepts exactly one heading — <h1> through <h6> — accompanied by paragraphs. It ties a subtitle to a heading without inventing a second heading level that would muddle the page's hierarchy.
That is precisely the gain: the subtitle sits visually next to the heading and structurally outside the heading hierarchy, which stays clean for anyone navigating from heading to heading.
<hgroup>
<h1>The HTML Herbarium</h1>
<p>Thirty native elements, pressed one page each</p>
</hgroup>