From Wikipedia, the free encyclopedia

An application programming interface (API) is a source code based specification intended to be used as an interface by software components to communicate with each other. An API may include specifications for routines, data structures, object classes, and variables.

An API specification can take many forms, including an International Standard such as Posix or vendor documentation such as the Microsoft Windows API, or the libraries of a programming language, e.g. Standard Template Library in C++ or Java API.

The practice of publishing APIs has allowed web communities to create an open architecture for sharing content and data between communities and applications. In this way, content that is created in one place can be dynamically posted and updated in multiple locations on the web.

Photos can be shared from sites like Flickr and Photobucket to social network sites like Facebook and MySpace.
Content can be embedded, e.g. embedding a presentation from SlideShare on a LinkedIn profile.
Content can be dynamically posted. Sharing live comments made on Twitter with a Facebook account, for example, is enabled by their APIs.
Video content can be embedded on sites which are served by another host.
User information can be shared from web communities to outside applications, delivering new functionality to the web community that shares its user data via an open API. One of the best examples of this is the Facebook Application platform. Another is the Open Social platform.[7]