What is an API? (a candidate's question for self-preparation before an interview)

API (Application Programming Interface) is a set of rules and protocols that allows different software components to interact with each other. In simple terms, an API defines how one program can use the functions or data of another program without delving into its internal implementation.

For example, when you use a weather app on your phone, it contacts the weather server API to get the latest data. The API describes what requests can be sent, what data to expect in response, and how to handle errors.