Joomla template have the ability to provide site users with customisable parameters. This gives the template designer a great deal of flexibility in allow the user to have few or many options by which to display the template. Parameters can be used to add additional features, like fancy menu systems, or control the size and shape of the web site in the browser, such as allowing for fixed or fluid width templates.

A template could include language files to translate parameter labels and meta descriptions, or it could use static labels in the master index file. Each of these cases requires a language file to be in a specific location with a specific naming convention.

Each template requires an XML meta file named templateDetails.xml. This file contains descriptive information about the template, the files used to install the template and optionally the module positions that are defined and template parameters.

Joomla allows for a template to display via the index.php file, but it also allows for a reduced version via a file named component.php that resides in the template folder. This file is used most commonly when the Print View button or link is clicked. A popup window is displayed which just shows the output of the component with minimal embellishment.

Joomla ships with a system template that contains many default elements used by the Joomla application. This is a template in its own right, having all the required elements to make it operate (albeit with poor aesthetic value and lacking the display of modules). However, the template lacks the XML meta file so cannot be selected from the Administrator Template Manager. That said, this template should never be removed either the frontend or backend template folders as parts of it are generally called upon by other core and third-party templates.

The master template file, index.php, is the file that is loaded by Joomla and controls all subsequent output. Any Site or Administrator template there are a number of common elements.

If the eyes are the windows to the soul, then the Joomla template is the window to the web. It is the vehicle by which output is arranged and displayed as a visitor browses your site. The template is made up of three different types of output: