H1 Headers

The header title, or the <h1> tag in HTML, will usually be the title of a page or blog post, or other emphasized text on the page.  It will usually be the largest text  on that page.  There are other header tags in HTML such an h2, h3, h4, etc.  Each can have a lesser degree of importance on the page, but it really depends on how your web developer designed your website layout.