JSON (JavaScript Object Notation) is a lightweight data-interchange format that is easy for humans to read and write, and straightforward for machines to parse and generate. It is commonly used to transmit data between a server and a web application, serving as a standard format for structured data. JSON represents data as key-value pairs, arrays, and nested objects, making it flexible and widely compatible with most programming languages. Its simplicity and efficiency have made it a popular choice for APIs, configuration files, and data storage.