What’s the difference between a REST API and a RESTful one? Is there a difference? This sounds like the kind of academic question that belongs on Reddit. But then you find yourself in a design session, and the person across the table is raising their voice.
The short answer is that REST stands for Representational State Transfer. It’s an architectural pattern for creating web services. A RESTful service is one that implements that pattern.
The long answer starts with “sort of” and “it depends” and continues with more complete definitions.