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
<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.