Templates give your site its look and feel. They determine layout, colors, type faces, graphics and other aspects of design that make your site unique. Your installation of Joomla comes prepackaged with four templates.
Beez 5 is an html5 implementation of a Joomla! template. It uses a number of html5 techniques to enhance the presentation of a site. It is used as the template for the Fruit Shop sample site.
Atomic is a minimal template designed to be a skeleton for making your own template and to learn about Joomla! templating.
Milky Way is the default template for Joomla! 1.5. You can find all of the 1.5 component layouts in the _html folder if you need them for your upgraded sites.