What is Application Program Interface (API)? 

An application program interface (API) is code that allows two software applications to communicate. It defines the correct and most efficient way for developers to request services from an external application and expose data within different contexts.

What can we use APIs for? 

APIs are intended to connect computers, systems, or software applications to each other; never users, except for the developer incorporating it into another software application. APIs are made up of different components which act as tools or services that can be “called” by the connecting application.

For example, a financial API could connect a database and an accounting application, pulling financial data automatically from the database into the application or vice versa.

They’re typically used to connect two previously unconnected applications for a custom purpose.