Many websites have a title and a tagline or subtitle. So for making the main heading and subtitle into one logical unit, the main heading and subtitle can be grouped in the
new <hgroup> element:

<a href="/"><img src=logo.png alt="home"></a>
<h1>My interesting blog</h1>
<h2>Tedium, dullness and monotony</h2>

The header can also contain navigation. This can be very useful for site-wide navigation, especially on template-driven sites where the whole of the
element could come from a template file.

There can be multiple <header>s in a page.
Related Tutorial
6. <nav>
7. <aside>
10. <article>