First, Let’s Define an API
An API (or “Application Programming Interface”) is a software intermediary for an application or service that enables other applications or services to send them requests and receive responses to those requests. The API will define the terms of the request and response such as the structure of the data, the data required, the protocol, and security settings.
An API makes it easier to integrate applications and services as the API forms a “contract” governing the communication between them. This gives developers certainty when integrating systems and can also enable larger monolithic services to be broken down into smaller independent services with defined interfaces.