The document discusses how to create custom themes for websites built using the langoor.net website builder platform. It explains that themes define the overall look and feel through styling guidelines. It outlines the default layout structure that langoor.net websites use, including areas like headers, footers, sidebars, and main content. It also discusses how all elements on the site are considered widgets that can be styled. The document provides examples of how to style elements like the page body, container wrapper, and headers by modifying CSS properties. It emphasizes that theme creators can customize styles and use class names to style different types of widgets like navigation menus.