APIs (application programming interfaces) are a big part of the web. In 2013 there were over 10,000 APIs published by companies for open consumption 1. That is quadruple the number available in 2010 2. With so many companies investing in this new area of business, possessing a working understanding of APIs becomes increasingly relevant to careers in the software industry. Through this course, we hope to give you that knowledge by building up from the very basics. In this chapter, we start by looking at some fundamental concepts around APIs. We define what an API is, where it lives, and give a high level picture of how one is used.
I found this downloadable e-book a while back at Zapier’s resource page, which has some other interesting things, but this overview and layout of APIs seemed fairly simple but powerful for folks interested in the topic.