In case you're not familiar with how a traditional CMS is structured versus a headless CMS, here's some background information to help get you oriented.
Traditional Wagtail
Traditional Wagtail puts all of your eggs in one nest: your backend code (the code that manages all your content and data) is strongly connected to frontend code (the code that powers how the people sees your content) on a single server or container. Having everything in one place makes it easier to test and troubleshoot your code all at once.
Headless Wagtail
With Headless Wagtail, you don't have to put all your eggs in one nest. Your eggs, which are different pieces of your code in this analogy, can be distributed to multiple nests, which are servers or cloud containers for hosting your code. Although the backend and the frontend can be distributed to different locations, they're still connected, but they're connected by an application programming interface (API). The frontend, whether it's a website, a mobile phone app, or a smartwatch app, can collect content from the same backend using the API and display it specifically for a particular device or app. Some common frontends that have been paired with Headless Wagtail include Next.js and Gatsby.
If you need more guidance about whether Headless Wagtail is right for your organisation, see our Guide for Decisionmakers.