In web design and document formatting, a header refers to the top section of a webpage or document. This area typically contains key information such as the website's logo, the main navigation menu, and sometimes contact details or social media links. In web development, the header is part of the HTML structure of a page and is often coded within tags. It plays a crucial role in branding and navigation, helping users understand where they are on a website and how to access other parts of it. Headers are designed to be visually appealing and functional, providing users with a consistent and easily recognizable reference point across all pages of a website.