Joomla is a free and open-source content management system (CMS) for publishing web content. It is built on a model–view–controller web application framework that can be used independently of the CMS
Joomla is written in PHP, uses object-oriented programming (OOP) techniques and software design patterns, stores data in a MySQL, MS SQL, or PostgreSQL database, and includes features such as page caching, RSS feeds, printable versions of pages, news flashes, blogs, polls, search, and support for language internationalization.
Joomla extensions extend the functionality of Joomla websites. Five types of extensions may be distinguished: components, modules, plugins, templates, and languages. Each of these extensions handles a specific function.
- Components are the largest and most complex extensions. Most components have two parts: a site part and an administrator part. Every time a Joomla page loads, one component is called to render the main page body. Components produce the major portion of a page because a component is driven by a menu item.
- Plugins are advanced extensions and are, in essence, event handlers. In the execution of any part of Joomla, a module or a component, an event may be triggered. When an event is triggered, plugins that are registered to handle that event execute. For example, a plugin could be used to block user-submitted articles and filter text.
- Templates describe the main design of a Joomla website. While the CMS manages the website content, templates determine the style or look and feel and layout of a site.
- Modules render pages in Joomla. They are linked to Joomla components to display new content or images. Joomla modules look like boxes, such as the search or login module. However, they don’t require html in Joomla to work.
- Languages are very simple extensions that can either be used as a core part or as an extension. Language and font information can also be used for PDF or PSD to Joomla conversions.