The Joomla Template system is amongst the easiest to learn in the Content Management System family.

Templates are located in the /templates directory. The following shows a typical directory structure for a template:

/templates
 /basic_template
  /css
   template_css.css
  /images
  index.php
  template_thumbnail.png
  templateDetails.xml

This is the minimum set of files you need to make a template. The filenames must be adhered to as each one is expected by the core script. Note that while there are no images shown in the /images directory, this is typically where you would place any supporting images for your template, like backgrounds, banners, etc. Let's have a look at each of these files.

index.php

This is the template layout file.

template_css.css

The css stylesheet for the template.

templateDetails.xml

This is a metadata file in XML format.

template_thumbnail.png

A reduced screenshot of the template, usually around 140 pixels wide and 90 pixels high.

This tutorial information is from www.joomla.org which is the home of Joomla.