A headless CMS, as opposed to a traditional CMS, omits the frontend and is not bound by a specific delivery channel, such as a website. There is no presentation, no frontend development toolset out-of-the-box. In other words, there is no head – hence the name. In a headless platform, the content is made available to be consumed via APIs and you can have anything on the receiving end: websites, mobile apps, AR and IoT devices and various integrations with third-party systems.
Unlike Headless, a Decoupled CMS has kept the publishing tools of traditional content management, meaning it has a frontend layer and frontend development tools are available right out of the box. A decoupled CMS has an architecture that clearly separates the management and storage of content from the pages and templates that display it. That is to say, the presentation (frontend) is decoupled from the backend. The two layers communicate via APIs. A set of endpoints expose the content to one or many consumers, from websites that can be developed with the built-in toolset (widgets, templates and the like) to various platforms and frontend frameworks that can take in and interpret the data in the API responses.