Application Programming Interface is a formalized set of software calls and routines that can be referenced by an application program to access supporting system or network services.

The correct answer to the question “What is API (Application Programming Interface)?” is:

An API (Application Programming Interface) is a set of rules and protocols that allows one software application to interact with another. It defines the methods and data formats that applications can use to communicate with each other. APIs are used to enable the integration of different software systems, allowing them to work together and share data. APIs can be web-based, operating system-level, or library-based, providing a way for developers to access the functionality of a system or service without needing to understand its internal workings.