What is Joomla!
Joomla! is a free open source CMS (for Content Management System) which allows you to build, and to manage, websites without any particular knowledge in programming languages.
Joomla! actually provides a friendly user's interface which allows you to easily create, manage and publish your content on your website.
So, all you need is to take in hand this user's interface to create and manage your website online
Joomla! provides natively many functionalities (such as users management, a multilinguale system, a banner component, a Tags system, a search engin, etc) which allows you to create very complete websites.
However, some projects require additionnal functionalities. For that, no problem, the Joomla! Community offers thousands of extensions (commercial or free of charges) to meet your specific needs.
On Kiwik.net, you'll find some documentations (as books, tutorials, etc)