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 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 an inherent presentation layer and frontend components 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 frontend is decoupled from the backend. The two layers communicate via APIs, which expose the content to one or many consumers, from websites that can be developed with the built-in toolset (pages, widgets, templates) to various platforms and frontend frameworks that can consume the data in the API responses.