Application Interface Definition
An application interface (also referred to as an application programming interface (API) is a set of rules and protocols that describes how two software programs or systems communicate with each other. The application interface serves as an intermediary between two systems as they exchange data.
Application interfaces allow third-party developers to access the features of a specific software platform. They also enable various software applications to integrate with one another.
APIs are implemented as a set of programming instructions that other applications or systems can access by calling them with a predetermined set of parameters and syntax. Web APIs, which are accessed via HTTP over the internet, and database APIs, which let applications access and modify information stored in databases, are a couple of the more popular kinds of APIs.