Template Manager is where you can set what template you want to use for your Front End and for your Administrative Interface.

A Template is a group of files that control the look and feel of your website.  It will have the basic page layout with the Positions defines.  It works with your Joomla installation by pulling in the content and modules that you have created and present them with the defined layout and styled using stylesheets.

The Template resides in your site files under the template folder.  Joomla 3 comes with four templates included. There are two templates to choose from to control the look and feel of the Front End. These are Protostar and Beez3. And there are two templates available to control the look and feel of the Back End, isis and Hathor.

You can also choose from hundreds of 3rd Party Templates.  Some of these are free, most require a payment. You can purchase a single Template or if you are a Developer of many sites, you can buy subscriptions that let you choose from multiple templates that you can use per the agreement of the subscription. You can even create you own custom template if you understand the PHP behind the Joomla system.

When you go into the Template Manager you will see the default Styles screen that lists the installed Templates. The default Templates will have a yellow star.  You can change the default template simply by clicking on the star for that Template.

The Protostar Template is the default Front End template.  It has a very simple and clean look.  It uses Bootstrap to make it Responsive, meaning that it will easily adjust to the various screens of mobile devices without a great deal of stylesheet modifications. Protostar does not give you an extensive Administrative Interface, so changing the look of the site will take some knowledge of CSS and modifying the template.css stylesheet or adding your own. To get a good idea of what Protostar is all about, visit the Zemplate website - bj.zemplate.com.

The other option for the Front End is Beez5. Beez5 is developed by Angie Radtke, who has worked with Joomla for some time and has written "Joomla! Templates". Beez3 has a more extensive list of Module Positions and they are named with the location of the position, ie Left Middle and Right Top. Beez5 also has Responsive styling and will work on various Mobile devices.

It is best to figure out which template you want to use early on in your sites development. As you modify you stylesheets, they may refer to <div> tags that are only present in that template.  Also, if you were to change to a new template midstream, you may find some of your modules have gone missing. They aren't gone from the database or from the Back End, but the new template may have different Positions. The modules may not have the new Position names specified and Joomla doesn't know where you want to put them.

3rd Party Templates

3rd Party Templates come in a wide variety of looks and give you more control over the template in the Back End as far as column locations, fonts, color schemes, etc.

You will download the 3rd Party Template form the developers site to your own computer.  You can then upload and install them using Extension Manager.  Once installed, return to Template Manager and click on the starr next to the Template name to set it as the default. If you click on the Name of the Template in the list, you will get to screens where you can edit many of the settings for the Template depending on how the 3rd Party Developer set up the controls.

Click here to see the joom3 article on Understanding Templates...