Traditionally, the backend of a CMS has been solely focused on content collection — allowing the user to perform tasks such as creating and formatting text, linking between pages and uploading images.
The front end of the system, or the ‘head’, then takes the content and publishes it to the user.
To decouple the CMS is to separate the content collection and the content delivery function. Decoupled or headless systems focus exclusively on content creation and do away completely with that publishing layer. Instead, developers can use Application Programming Interfaces (APIs) to build websites and applications using their programming language or toolkit of choice — meaning they can republish the content on an array of devices or channels.