This document provides an overview of Content Management Systems (CMS) and the open source CMS Joomla. It defines what a CMS and Joomla are, lists common versions of Joomla, and describes why Joomla is used and for what purposes. It also summarizes key Joomla extensions like components, modules, plugins, languages and templates. Finally, it provides tips for using Joomla and examples of Cambodian websites powered by Joomla.