Explain what JSON Web Token is and its main purpose in authorization systems.

JSON Web Token (JWT) is a compact, URL-safe way to transmit information between parties as a JSON object. The main purpose of JWT in authorization systems is to securely transmit user data and access rights after successful authentication.

JWT consists of three parts: header, payload, and signature. The signature ensures that the token has not been altered.

Example of usage: after a user logs in, the server creates a JWT with user information and sends it to the client. The client then includes this token in subsequent requests, the server verifies the signature, and extracts data for authorization.

This allows the creation of stateless authorization systems, where the server does not store session state.