This document discusses WordPress's template hierarchy. It explains that WordPress uses different template files to display different types of content. For example, it will use home.php for the homepage if it exists, or index.php by default. For category pages, it will try category-slug.php, category-id.php, category.php, archive.php, and finally index.php. This logic is followed for other content types like single posts, pages, author pages, and more. The document provides examples of the template file names WordPress looks for in different situations.