What Does Application Programming Interface (API) Mean?
An application programming interface (API) is a set of protocols, routines, functions and/or commands that programmers use to develop software or facilitate interaction between distinct systems. APIs are available for both desktop and mobile use, and are typically useful for programming GUI (graphic user interface) components, as well as allowing a software program to request and accommodate services from another program.
Techopedia Explains Application Programming Interface (API)
An API can be seen as composed of two fundamental elements: a technical specification that establishes how information can be exchanged between programs (which itself is made up of request for processing and data delivery protocols) and a software interface that somehow publishes that specification.
The basic concept behind the API has existed in some form for the entire history of digital technology, as the interaction between unique programs and digital systems has been a primary objective for much of that technology's existence. But with the rise of the world wide web, and the subsequent turn-of-the-millennium dot-com boom, the incentive for this technology reached an unprecedented level.
The API became especially prominent in the burgeoning commercial sector of the world wide web in early 2000, when Salesforce.com incorporated the technology into its platform in order to help customers share and transmit data over their diverse business applications. Soon after that, eBay began rolling out similar technology, and with the rise of social media a few years later, companies like Flickr, Facebook, Twitter and Instagram began doing the same.