What is an API

In programming, an Application Programming Interface (API) is a set of subroutine definitions, protocols, and tools for building application software. It is a set of clearly defined methods of communication between various software components. A good API makes it easier to develop an itegration between systems by providing all the building blocks, which are then put together by the programmer. An API may be for a web-based system, operating system, database system, computer hardware or software library. An API specification can take many forms, but often includes specifications for routines, data structures, object classes, variables or remote calls. Documentation for the API is usually provided to facilitate usage.