Out of the box, Joomla! does a great job of managing the content needed to make your Web site sing. But for many people, the true power of Joomla! lies in the application framework that makes it possible for developers all around the world to create powerful add-ons that are called Extensions. An Extension is used to add capabilities to Joomla! that do not exist in the base core code. Here are just some examples of the hundreds of available Extensions:
- Dynamic form builders
- Business or organisational directories
- Document management
- Image and multimedia galleries
- E-commerce and shopping cart engines
- Forums and chat software
- Calendars
- E-mail newsletters
- Data collection and reporting tools
- Banner advertising systems
- Paid subscription services
- and many, many, more
You can find more examples over at our ever growing Joomla! Extensions Directory. Prepare to be amazed at the amount of exciting work produced by our active developer community!
A useful guide to the Extension site can be found at:
http://extensions.joomla.org/content/view/15/63/
Types of Extensions
There are five types of extensions:
- Components
- Modules
- Templates
- Plugins
- Languages
You can read more about the specifics of these using the links in the Article Index – a Table of Contents (yet another useful feature of Joomla!) – at the top right or by clicking on the Next link below.
ME 
EN