Headless CMS
A headless CMS stores and manages content but does not control how it is displayed, delivering it to any front end through an API.
In full
A headless content management system separates content from presentation. It provides an editing interface and a structured store, then makes the content available through an API to whatever front end requests it, rather than rendering pages itself using themes and templates. Traditional systems such as WordPress in its default configuration couple the two, so the CMS both stores the content and determines the markup. The headless approach lets the same content serve a website, a mobile app, and a digital display without duplication, and lets developers build the front end in whatever framework suits without fighting the CMS.
Why it matters
It gives an editorial team a clean interface for the parts of a site that change, while keeping design and structure under version control, so content updates cannot gradually degrade the design.