What is a Headless CMS?

I really enjoy discovering new stuff and sharing it with others that have the same interests as me. This one's for you:

A headless CMS is a content managing system that organizes content without the help of a frontend presentation layer eg. a website. This headless architecture focuses more on content delivery and storage rather than display methods, providing flexibility, responsiveness, and a better omnichannel approach.

I could dive more into the differences between a headless and traditional CMS, but I couldn't possibly reach the quality of this blog post:
https://moosend.com/blog/headless-cms/

Did you know about this type of CMS?