The hgroup element represents a group of headings.
one or more of: one h1 element, or one h2 element, or one h3 element, or one h4 element, or one h5 element, or one h6 element
A hgroup element must have both a start tag and an end tag.
any element that can contain flow elements
The hgroup element is typically used to group a set of one or more h1-h6 elements — to group, for example, a section title and an accompanying subtitle.
Uses HTMLElement.