A JSON Web Token, or JWT, is a JSON-based open standard for creating tokens that assert some number of claims. You can learn all about this technology on the website (https://jwt.io/). In a nutshell, this type of token is comprised of three sections, separated by a dot, in the format A.B.C. B is the payload, which is where we put the data and the claims. C is the signature, which is used to verify the validity of the token, and A is the algorithm used to compute the signature. A, B, and C are all encoded with a URL safe Base64 encoding (which I'll refer to as Base64URL).
Base64 is a very popular binary-to-text encoding scheme that represents binary data in an ASCII string format by translating it into a radix-64 representation. The radix-64 representation uses the letters A-Z, a-z, and the digits 0-9, plus the two symbols + and / for a grand total of 64 symbols...