The <header> element defines introductory content for a document or a section.
A header commonly contains a heading, logo, author information, navigation, or other material that introduces the content that follows. Because it can belong to the page as a whole or to an individual section, a document may contain multiple <header> elements—for example, one site header and separate headers for several articles.
The element became part of HTML5’s semantic markup vocabulary, which was designed to describe the structure and meaning of page content more clearly than generic layout containers. Its meaning is structural rather than visual: browsers do not require it to look a particular way, and CSS controls its appearance.
The <header> element is often confused with <head>. The <head> contains metadata, the title, stylesheet links, and scripts, while <header> is visible page-content markup. Likewise, <title> supplies the document’s browser-tab title; it does not create a visible section header.