Joomla! is an open source content management system platform for publishing content on the World Wide Web and intranets as well as a Model–view–controller (MVC) Web application framework. It is written in PHP, stores data in MySQL and includes features such as page caching, RSS feeds, printable versions of pages, news flashes, blogs, polls, search, and support for language internationalization.
So why do we like Joomla? Once your Joomla! site is up and running, anyone with basic word processing skills can update it by adding content, managing images and keeping company-critical data up-to-date via a simple, browser-based interface. And because it's free and easy to use, you can focus your resources on the bit that really matters - the content.
Now you can have the power to easily add new text, pictures and even edit flash movies using the user-friendly back-end. It is even possible to move modules into different positions quickly and easily leading to more dynamic and interesting websites.