JSON (JavaScript Object Notation) files are a lightweight data interchange format that is easy for humans to read and write. They are commonly used to store and transmit data between a server and a web application. The structure of a JSON file consists of key-value pairs, making it simple to organize and access information. JSON files are often used in programming languages like JavaScript, Python, and Java due to their compatibility and ease of use. They can represent complex data structures, including arrays and nested objects, which makes them versatile for various applications, such as APIs and configuration files.