What is This?
Caveat emptor: This information has not been updated since the Joomla! 1.5.3 release in April 2008.
This is some stuff I learned while attempting to upgrade my existing Joomla! 1.0.x templates to work with Joomla! CMS 1.5. There's nothing much original here. The information in the underlying pages was gathered from Developer Blogs, Documentation and various Forum Posts at the official Joomla! Project web site.
Very Brief Overview
Joomla! is an Open Source (GPLv2) CMS that uses modules, components, and plugins to organize, manipulate and present content. A complete discussion of these constructs is beyond the scope of this discussion. If you are new to all this, you can find more information about this stuff at Joomla.org:
If you are still interested in this stuff after reading the above, read the underlying pages and learn arcane techno-factoids about stuff like templateDetails.xml, index.php, template_css.css.and last, but certainly not least, the core css classes.