Don’t get fooled by too many articles out there that make JWT sound more complex and complicated than it actually is. In simple words, JWT is a simple format that aims to transfer claims between two parties in a compact and secure manner. A claim is a key-value pair that asserts something about a subject.
The diagram below will give you a very simple idea of how a JWT is layered. It is a set of claims as a JSON object, that is secured by a JWS (JSON Web Signature) or a JWE (JSON Web Encryption) layer.