The style tag is used to define style information for an HTML document.
Inside the style element you specify how HTML elements should render in a browser.
Each HTML document can contain multiple style tags.

Example:

<style>
h1 {color:red;}
p {color:blue;}
</style>

You can also use this tag in a div or an id, example:

<div class="myclass" style="parameter:setting;"></div>

Source: http://www.w3schools.com/tags/tag_style.asp