The header is used to define the introductory information of a page, section or article. The header cannot be placed in a footer.
ARIA role attribute value: banner
This attribute should only be used once per page when the header element is not a descendant of an article or section.
The header element represents introductory content for its nearest ancestor sectioning content or sectioning root element. A header typically contains a group of introductory or navigational aids.
HTML 5.1 Nightly
You do not have to include a header in a section just a heading is ok