Definition

API is the programming interface of a software application that allows users of the application to write their own 'add-on' programs functionality. It also provides communication between the two platforms and allows data to be shared with customers and other external users. The capabilities offered by the API include features for creating simple applications, AI-related features, graphics generation, hardware resource management, etc.

Application

Social networks, for example, allow users through APIs to view and publish posts through their mobile apps. If you use an app like Facebook to send an instant message or check the weather on your phone, you are using an API.