What is JSON

Answer 1

JavaScript Object Notation or JSON is an open-standard file format that uses human-readable text to transmit data objects consisting of attribute–value pairs and array data types (or any other serializable value). It is a very common data format used for asynchronous browser–server communication, including as a replacement for XML in some AJAX-style systems.
[wikipedia]

Answer 2

JSON is one of the most important things to get a really good understanding of as it is the preferred way to transmit information. XML used to be the standard... now it is JSON.