Division. Defines a block of HTML. Commonly used to apply CSS to a chunk of a page. The <div> tag is used to group block-elements to format them with CSS. The difference between the <div> tag and the <span> tag is that the <div> tag is used with block-level elements whilst the <span> tag is used with inline elements.
<div id="navigation"> [stuff] </div> <div id="content"> [stuff] </div>