CSS stands for Cascading Style Sheets. CSS works in conjunction with HTML. In order to understand the purpose of CSS and how to use it, one must first understand how to use HTML.
The purpose of a CSS document is to define how the HTML elements will appear, to define their 'style'.
External style sheets, which can be saved in CSS files, were added to HTML 4.0 to solve a clutter problem. HTML pages were never designed to store large amounts of style information. This is where CSS comes into play.
