This document discusses using a headless CMS like Drupal or WordPress with GatsbyJS to build modern websites. It defines headless CMS as a back-end only CMS with a RESTful or GraphQL API to access content. GatsbyJS is introduced as a framework for building fast websites and apps with React. The benefits discussed are using GraphQL to centralize data access, leveraging Gatsby plugins and themes, and providing a better developer experience with modern technologies and separation of concerns.