What is Joomla

Joomla! is an award winning content management system for websites. Joomla! is written in the PHP programming language and uses a Mysql database system to store information.

Joomla! allows for administration of a website without knowing any html. It also acts as a framework where other people can easily extend its features.

Joomla! began as a project called Mambo, developed by Miro Construct Pty Ltd of Australia, and started in 2000.
In 2005, in a rift over licensing, most of the core programmers left to found Joomla!.

Joomla! is a free, open-source project using volunteer programmers around the world. It is licensed under GNU GPL v2 and owned by a non-profit group called Open Source Matters.

Joomla! version 1.0 was a near copy of Mambo. Joomla version 1.5 was a complete rewrite. Version 2.5 added many new features including fine grained access controls.
Version 3 continues the addition of features, stability and security.

Check out joomla.org.