Extensible Markup Language (XML)
A markup language and file format for storing, transmitting, and reconstructing arbitrary data. [Wikipedia link]
JavaScript Object Notation (JSON)
An open-standard file format and data interchange format that uses human-readable text to store and transmit data objects consisting of attribute–value pairs and arrays. [Wikipedia link]
JSON Web Token or JWT
An open standard for Authentication that uses a JavaScript Object Notation (JSON)-encoded token to securely represent claims between two parties. Typically, the tokens are used to represent an identity and its associations, such as a user and role or group. [Wikipedia link]