Joomla is one of the easiest-to-install content managers out there. Just copy the content of the ZIP file into the 'htdocs' folder on your Apache server, run the installation script, and you're ready to upload content onto the Internet.
Like other content managers, Joomla uses a module system that allows you to add new packets that complement its model: photo galleries, word processors, etc.
Another interesting feature is that you can use templates to change the look and feel of your site. There are dozens of templates designed specially for Joomla that are all available for free.
You don't need to know anything about programming to use Joomla. Everything is controlled from an intuitive control panel from which you can add users, change permissions, edit content, and much more.