What is JSON used for?
JSON is most commonly used in API's for serializing data that can be sent over a network connection in a structured manner. The JSON format is both human and machine readable and is used in many application to application operation. Where connection between backend and frontend application being a common use-case.
Is JSON an API?
JSON is not an API, API stands for Application Programming Interface and is the basis of any machine to machine operation. However JSON is common format used to serialize and structure data that can be used across an API.