This tutorial teaches how to implement a preview system when working with a headless CMS like Strapi, using Next.js for creating content previews. It covers setting up the necessary packages for developing a Next.js website and designing an articles page that fetches your articles from Strapi CMS. The tutorial also explains how to configure the Next.js Preview API for viewing drafts on your Next.js website, and how to add a preview button in Strapi Content Manager.