Heading elements (h1 through to h6) are used to give structure to the content of your page. They're important for SEO, make your pages more readable and, of course, also help people that use assistive technologies navigate through your page. Somewhat less known are landmark elements. These are elements that are used to define the structure of your entire HTML and you probably know some of them already: nav, main and footer are all landmark elements (well, most of the time. We'll get to that.)
