A JSON Web Token (JWT) is an Internet standard for securely transmitting information as a JSON object, which can be signed and optionally encrypted. The text explores the creation, verification, and decoding of JWTs using the JavaScript library jsonwebtoken. JWTs encode JSON data along with metadata like the issued time (iat) and can be verified using a secret to ensure authenticity. While anyone can decode a JWT to view its contents, the signature ensures that the data hasn't been tampered with. JWTs are commonly used in authentication systems where they store user metadata without requiring external state management. The document also discusses signing options, including expiration times (exp), issuer claims (iss), and different algorithms, highlighting the importance of specifying expected algorithms to prevent security flaws. JWTs can be invalidated by using short-lived tokens, maintaining a cache of invalidated tokens, or rotating the secret, although these methods each have trade-offs. The text encourages further exploration of JWT concepts by examining documentation from other libraries like PyJWT.