One important step ahead brought by HTML5 is the introduction of new elements which enable the creation of web pages with more explicit semantics, leveraging the traditional usage of the semantically-neutral <div> tag:
<article> which represents a blog article, forum post or similar.
<aside> which indicates that the content is tangential to the main content of the page, for example ads or similar.
<nav> which indicates that such a block gives the main navigation points for a page.
<figure> to represent figures on a page
<header> to indicate header content
<footer> to indicate footer content such as copyright information, additional links, etc.