Joomla is an open source content management system (CMS) that is free, powerful, and robust. It has a large community of users and developers and powers websites for organizations like MTV Networks, Harvard University, and IHOP. While Joomla has advantages like its flexibility and powerful admin interface, it also has some disadvantages such as a steeper learning curve compared to WordPress and the potential for slow loading times. WordPress may be better suited for simpler sites that don't require the full feature set of a CMS.