From Joomla! Documentation
A template controls the overall look and layout of a site. It provides the framework that brings together common elements, modules and components as well as providing the cascading style sheet for the site. Both the front-end and the back-end of the site have templates.
When Joomla! is first installed several templates are automatically included. You can find many more templates at other websites. Some are available without charge under various licenses, and some are for sale. In addition, there are many developers available who can make custom templates. You can also make your own template.
Templates are managed with the Template Manager, which is located on the Extensions menu in the back-end (administrator) area of your site.
Why does Joomla! use templates? [A real beginners guide!]
The way Joomla! is designed separates out the key tasks involved in producing a website for efficient maintenance of the software. One of these tasks is to create the aesthetic (the look, feel and layout) of the site. This includes making decisions such as which content elements (components, modules and plugins) you may want to place in any given page.
When producing a web page, the location of most elements will stay the same (menus, banner locations, sidebars etc.). Additionally, you will want to create the same look (fonts, header styles, colour scheme etc.) for every page. For some parts of the site you may want to alter the general feel to indicate a different purpose for those pages (such as a blog section). A little planning is required for this, but once you have settled on the overall layout for your site, you then have the task of producing each page of content.
And that’s where the template comes in. You can either write all the code for each page separately, or use a template for each major section of your site so that when you want to create a new page you simply “fill in the blanks”. Okay, perhaps it's not that simple, but this tutorial is designed to give you a step by step guide for effective template use, starting with how to use one and ending with how to create one for yourself.
- Use one of the templates supplied with Joomla!
- Download one of the many free offerings from the Internet.
- Pay for one to be modified or produced from scratch if your needs cannot be met any other way.
Summary – a template controls the look of your site and at the same time allows the website administrator focus more on the actual content.