What is an API?
API is the acronym for Application Programming Interface, which is a software intermediary that allows two applications to talk to each other. Each time you use an app like Facebook, send an instant message, or check the weather on your phone, you’re using an API. When you use an application on your mobile phone, the application connects to the Internet and sends data to a server. The server then retrieves that data, interprets it, performs the necessary actions and sends it back to your phone. The application then interprets that data and presents you with the information you wanted in a readable way. This is what an API is - all of this happens via API.
Common, everyday examples of this could be when paying with Klarna at your e-commerce checkout, logging in with Facebook or Google on different sites and devices or booking a flight or hotel through a site like Expedia. All of these examples use APIs to work properly and for the applications to communicate to each other.
List: 5 awesome uses of APIs
1. NASA

"NASA API weather report Mars"
2. Houndify
3. Real time air quality index

"API Pollution Index"
4. Google
5. Human API
Human API is an exciting health data platform that gives people a free, simple, transparent and secure way to connect and share health data with companies they trust. This gives a great platform for physicians and healthcare organizations to gather and verify information. Read more on HumanAPI.

"Human API example "