The HTML <header> element represents introductory content, typically a group of introductory or navigational aids. It may contain some heading elements but also other elements like a logo, a search form, an author name, and so on.

Content categories Flow content, palpable content.
Permitted content Flow content, but with no <header> or <footer> descendant.
Tag omission None, both the starting and ending tag are mandatory.
Permitted parents Any element that accepts flow content. Note that a <header> element must not be a descendant of an <address>, <footer> or another <header> element.
Permitted ARIA roles group, presentation
DOM interface HTMLElement