What is Joomla

Joomla! is an open source content management system platform for publishing content on the World Wide Web and intranets as well as a Model–view–controller (MVC) Web application framework. It is written in PHP, stores data in MySQL and includes features such as page caching, RSS feeds, printable versions of pages, news flashes, blogs, polls, search, and support for language internationalization. Joomla is used by over 0.2% of the top 10,000 most popular websites on the internet.
Deployment: Joomla can be installed manually from source code on a system running a web server which supports PHP applications. Manual installation usually requires more time and experience than other alternatives such as installing Joomla from a package management system or using a TurnKey Joomla appliance which pre-integrates Joomla and its dependencies as a ready-to-use system
ou can have running, professional website in couple of hours. There are numerous web hosting companies who provide a control panel which automates the deployment of a basic Joomla web site. Several noteworthy hosting companies that include Joomla deployment are GoDaddy.com, Siteground.com, Web.com, DreamHost.com, HostGator.com, BlueHost.com and hundreds of others.
Criticism : In keeping with the stated vision of "Software that is free, secure and of high-quality," any third-party extensions submitted to the official Joomla! Extension Directory (JED) web page, which was already packed with over 3800+ extensions listed as of December 15, 2009, must now also conform to the GPLv2 license for free distribution.

* Joomla! 1.5.x will work with any number of domain names in one installation, but showing different content for each one requires the use of third party extensions or modifications to the core or server configuration. However, each page can be configured to use a different template and/or can be made accessible via different domains using the "external link" menu option in Joomla! which appears as a different site to the user.
* Bi-directional language templates that make use of Joomla!'s comprehensive bi-directional language support, other than those included with the standard install, are less common, and many don't allow for easy switching between LTR and RTL language formats. Most other templates can be easily modified via Joomla!'s built-in template editor.
* Access control granularity beyond Joomla! 1.5.x's nine built-in user groups currently requires the use of third-party extensions, although this is planned for Joomla! 1.6.
* Article organization beyond Joomla! 1.5.x's current Section/Category hierarchy requires the use of third party extensions, however flexible category structure support is planned for Joomla 1.6
* All "pages" (views) in Joomla! are referenced in the system by a unique ID number assigned by way of its "menu item" (link). So, for any page to function properly as part of the framework, it must have at least one menu item associated with it, whether that menu item is visible or not. This may be initially confusing to some newcomers.