Overview

WordPress uses the query string to decide which template or set of templates should be used to display the page. The query string is information that is contained in the link to each part of your website.

Put simply, WordPress searches down through the template hierarchy until it finds a matching template file. To determine which template file to use, WordPress:

1. Matches every query string to a query type to decide which page is being requested (for example, a search page, a category page, etc);
2. Selects the template in the order determined by the template hierarchy;
3. Looks for template files with specific names in the current theme’s directory and uses the first matching template file as specified by the hierarchy

Examples

If your blog is at http://example.com/blog/ and a visitor clicks on a link to a category page such as http://example.com/blog/category/your-cat/, WordPress looks for a template file in the current theme’s directory that matches the category’s ID to generate the correct page. More specifically, WordPress follows this procedure:

1. Looks for a template file in the current theme’s directory that matches the category’s slug. If the category slug is “unicorns,” then WordPress looks for a template file named category-unicorns.php.
2. If category-unicorns.php is missing and the category’s ID is 4, WordPress looks for a template file named category-4.php.
3. If category-4.php is missing, WordPress will look for a generic category template file, category.php.
4. If category.php does not exist, WordPress will look for a generic archive template, archive.php.
5. If archive.php is also missing, WordPress will fall back to the main theme template file, index.php.

Visual Overview