For question regarding Joomla 3.3.x of the Content Management System only. If the question is relevant to any Joomla 3 version.
For question regarding Joomla 3.3.x of the Content Management System only. Joomla 3.3.x is a STS (Short Term Support) version. Support ends one month after the next release of Joomla is released. One click upgrades to the next STS or LTS version is possible.
Both STS and LTS releases, once they have reached the GA (General Availability) status, are fully functional and ready to be used in production environment. The disadvantage of using STS releases is that you will need to update your installation of Joomla more often, while the advantage is that you will have access to new features and extensions earlier.
Joomla 3.0 was released on September 27, 2012. Originally, it was supposed to be released in July 2012; however, the January/July release schedule was uncomfortable for volunteers, and the schedule was changed to September/March releases (1).
- Responsive by default. The default templates (Front-end: Protostar, Back-end: Isis) are fully responsive, and Joomla was the first major CMS to achieve this. Twitter Bootstrap integration
- New admin interface. Big overhaul of admin interface to improve usability PostgreSQL support
The latest version of Joomla can be downloaded from http://www.joomla.org/download.html.
Instructions on how to install Joomla can be found at Joomla! Docs