The div Element
The div (short for "division") is a block-level element designed to hold a "block" of information. The div tag/element wraps around a whole section of content. A div may contain paragraphs, headings, tables, and even other div's. Think of a div as a container for an individual part or section of a web page. This makes div ideal for having different classes of containers. The div requires both an opening <div> and a closing </div>.
Div Styling
You can assign specific styling to the different div's used on a page with the use of an external style sheet or embedded styling through the class or id attribute and with inline styling.
Consider your entire web page as a single div. Inside this div you can have smaller div's that will hold different blocks of page content. Remember that you will be nesting the div's so be sure you close each div as needed in reverse of the opening order.
For example;
<div class="one">
<div class="two">
<div class="three">
</div><!-- close div three -->
</div><!-- close div two -->
</div><!-- close div one -->