Netlify CMS is a single-page app written in React, built on Git, and can be used with static site generators like Hugo or Middleman. It's designed to be minimal and easy to understand, allowing users to create, edit, and manage content without the complexity of traditional CMS applications. By setting up Netlify CMS locally, developers can experiment with its features and learn how it integrates with GitHub as a content database, enabling users to store and deploy their content efficiently. The CMS uses authentication services provided by Netlify for local development, allowing users to create, save, and edit posts while storing them in their remote Git repo on GitHub.