This simple car analogy will help you understand the difference between the template, Joomla, extensions, plug-in and modules.
The template is the car body and paint work which controls the visual presentation or look and feel of the website
Joomla is the car engine which powers the website and allows you to create user accounts, setup menus, categories, add and publish text plus images and basically manage the overall website functionality via the administrator control panel.
The lights, wind wipers, spark plugs are the 3rd party modules and plug-ins you can install via the website.
The car radio and sat navigation are the 3rd party extensions like a forum, photo gallery which you can install via your website
To sum up the template only controls the visual presentation or look and feel of the website.
All the other functionality is controlled by Joomla or 3rd party plug-ins, modules or extensions.
What is included in the template and how is it structured
Each Joomla template which you can download at the website comes in a zip file package format which can be easily uploaded and installed via the Joomla administrator area of your website.
Once the template is successfully installed at your website you can set it as the default design or style to change the look and feel of the site.
If the template includes support for additional built-in features then the built-in features can be updated via the control panel which comes supplied with the design.
The template is made up of the following directories and files
PHP files – The PHP files control the functionality, module positions plus other elements of the template
TemplateDetails.xml – The XML file is used to help Joomla understand the name of the template, version number plus the files and directories which need to be installed during the installation. The XML file also includes code used to setup the features the template supports via the control panel.
CSS files – The (CSS) Cascading Style Sheet files which are located in the CSS directory control the look, feel and style of the template to ensure it renders correctly across both desktop and mobile web browsers
HTML overrides – The HTML over ride files are made up of PHP and HTML files which are stored in the HTML directory and override the default Joomla content, module and other views.
Images Directory – The images directory include all the images used by the template
Language files – The language files are stored in the language directory