The Divi theme is the most popular premium WordPress theme in the world (stats from BuiltWith.com) and the most powerful theme in the campuspress theme collection, including the visual drag & drop Divi page builder and pre-made layouts.
The video above should help you get up to speed with using the Divi theme.
Please note: it is not compulsory to use this theme for your blog. The Divi theme has been used in this template to provide and easy integration into the WordPress platform. If you decide to use another theme, please be aware that some of the pre-made elements of your blog my not work in other themes.