As you will recall from last post, "Content Management Systems and an Introduction to Joomla," it's hard to find a Joomla-powered website that has not added functionality beyond the basics with some sort of extension. The word extension collectively describes components, modules, plugins, and languages.

There are several hundred extensions available both free and commercially from third-party providers. You can find out more about them at extensions.joomla.org and www.extensionprofessionals.com.

Currently, most extensions work with the 1.5.X version of Joomla. Because it is so new, there are currently not many third-party extensions that run natively on 1.6. As it goes though its roadmap cycle of Beta to Release Candidate to Stable, we will hopefully see third-party extensions upgraded to work on the new version.

What Are Extensions?

Extensions are installable packages that extend the core functionality of Joomla in some way. There are five types of extensions:

1. Components : A component is the most complex type of extension. It is some sort of mini-application that usually renders content in the main body (large middle column) of the page. The core content component (com content), for example, is the mini-application that shows all your articles in some way. Another example might be a forum component that shows boards, threads, and so on. Not all components are about content; some handle a complex function. For example, the registration component (com registration) handles user registration.
2. Modules : Modules are usually much smaller and less complex than components. They also usually appear around the edges of the main body, in the header, side columns, or footer and are small extensions that do small tasks. For example, the Latest News module shows links to the most recent articles that have been added to the site. Often, a module will work with a particular component. For example, the login form module allows site visitors to log in to the site.
3. Plugins : A plugin (formerly called mambot) is a special piece of code that can be used across the site and runs when a page is loaded. An example is the email cloaking plugin, which hides email addresses with JavaScript so spam robots cannot see them.
4. Templates : Templates control the graphical look and feel of the site. They usually include colors, graphics, and typography.
5. Languages : By installing a language pack, it is possible to internationalize Joomla to a different language. All of the words that are part of Joomla (like where it says "Read More") will be displayed in the chosen language.