Joomla CMS or 'Content Management System' is an open source programme that allows you to change the text and images on your website without any technical training whatsoever. It powers millions of websites and applications of all types: think anything from personal blogs to corporate portals and intranets. Joomla is built with PHP and MySQL.
Joomla requires a lot more technical skill than WordPress. But once built it is simple to use. (See image below)