What is an API?

It's possible you've heard the name—perhaps about the time your eyes glazed over and your desire to nap kicked into full swing.While it might at first seem boring, API's are at the heart of the modern internet and are largely responsible for much of the information exchange that happens online.

API stands for Application Programming Interface. It provides a way for different systems to speak with one another, often unlocking potential for greater information or improved utility.

APIs are only valuable if they connect with data. Assuming there is a store of information somewhere worth knowing, an API can allow access to that data. Developers (programmers) connect with APIs to retrieve and sometimes create or edit data. They then also create ways for that data to be visualized for the end user—perhaps as a recipe card or as an eLearning record. 

Websites, phone apps, and even thermostats can use APIs.Generally speaking, APIs return their data in agreed-upon formats such as XML ( eXtensible Markup Language) or JSON (JavaScript Object Notation), although this is not always the case. When the languages are standard, often the data definitions between systems do not fully align. Even systems APIs are subject to human interpretation at the point where two systems come together. A well-documented API is therefore deeply appreciated by developers.

Every time you pin a post, book a flight, reserve a hotel or check your calendar, you are likely triggering the use of an API (or several). Knowing a product can ship from a location near you within the timeframe you've ordered it for and taking the payment for that order online almost certainly invokes several APIs along the way.

Whatever the end use of the data, exposing it is the job of an API.

Further Resources:

What is an API (In English please)

What is the meaning of API?