Joomla is an open source content management system. This means that anyone can write an extension of the core Joomla software program and the extension will work with it as if it was an original aspect of the software. With this being said, there are a wide variety of extensions available on the market today that can take the basic Joomla programming and extend it to unlimited possibilities.
Extensions include components, modules, plugins and templates. We will focus on the themes. Joomla designs are what will define the style and layout of your website. There is a large variety of templates available on the market because of the open source concept. You will just need to know about the different types of templates that are available before you make your decision.
There are two different types of Joomla templates. There are the back end templates and these templates define the style and layout of the website as the Administrator, editors, webmaster, and so on will see whenever they log into their accounts. This is the "back side" of the website. Very few people will have access to the back end. Then there are the front end templates. These templates will define the style and layout of the front end side of the website. This is the side that the visitors will see whenever they either log on to the page or just stop by for a visit.
Back end designs will help you to arrange your information, access and controls to make your life much easier. With the initial Joomla download, you will receive one back end template; however, back end themes are available all over the internet for either free or for purchase. You could even write your own if you can find no other back end template that will suit your needs.
Front end designs will give the feel to the website, the side that your visitors will see. When searching the web and visiting websites that is the front end of the site that you are seeing. There are literally thousands of Joomla templates available for the front end. You can choose literally anything that you want. If you can dream a design up in your head, it can be made and it probably already has. It may take you awhile to find the perfect one after you sift through the thousands that are available. If you still can't find it, you can either have one modified or one made specifically to meet your needs.
The front end guides are uploaded and installed through the back end of your website. You can install several different ones (2 actually come with the initial Joomla software) and keep them available. You can assign a different guide to every page or you can use just one. Guides can only be used for one website, so if you own more than one website, you will have to download the templates more than once, if you want to use the same one. The options are limitless, so have fun!