On the Internet there are two basic types of websites. Those written in plain HTML and those who utilize a Content Management System (CMS) to organize and display the information contained in the site. They both serve the same purpose but do it in VERY different ways. For some people plain HTML may be enough for simple, basic information based websites. For those who want more control, flexibility, and dynamic content a Content Management System may be the way to go. This article details the basics of what CMS systems are and why they may be appropriate for even beginning web site designers.
More here about CMS Systems.