Templates are themes that control the look and feel of your website. You can completely change the way your website looks without modifying any of your content, just by installing a different template. There are lots of free and commercial templates available for Joomla.

Modules are little windows of content that are usually placed around the edges of your site's pages, while the main content goes in the middle area. For example, menus are displayed in modules - usually at the top or left of the page, but they can go anywhere. Banners, google adverts, copyright notices, calls to action, anything really, can go in a module - if you want it displayed in a discrete box of its own outside the main content area.

Mambots (or 'Plugins' in Joomla 1.5) are little programs that are run immediately before the content of a page is rendered and sent to the browser. They are useful for replacing parts of your content - for example, if you want all occurrences of your company name to appear in a bold typeface, a mambot could be developed that would search and replace your company name with a bold version. Mambots are also used for adding images or page breaks to your content. Any time you need some dynamic piece of functionality to appear within a content item, you need a mambot.

Components are the biggest and most complex type of extension. They generally output their content in the main area of your web page, and usually have some administration features in the Joomla back end as well. Components are very versatile, and allow you to add a wide range of features to your site, such as eCommerce, forums, events calendars, forms, etc.