A JSON Web Token (JWT) is a compact, secure, and self-describing format for exchanging information between parties. It consists of a JSON structure that has three parts: the header, the payload, and the signature.
Header: The header contains metadata about the type of the token and the signature algorithm used.
Payload: The payload contains the actual claims or information carried by the token. These claims can include user data, roles, permissions, etc.
Signature: The signature is used to ensure that the token has not been tampered with. It is created by signing the header, payload, and a secret key (known only to the issuer of the token).
JWTs are commonly used for authentication and authorization in web applications. For example, they can be used to authenticate users after login and grant them access to specific resources by being stored in HTTP headers or HTTP cookies and exchanged between the client and the server.