A comprehensive introduction to understanding what an API is

If you are trying to become familiar with the technology that relies on the interconnection between applications and services, probably you have heard the term API several times. If you still do not know what it is, we can introduce it by saying that API is the abbreviation of what is known as Application Programming Interface. Maybe this does not tell you much, but without the API, communication between online services and users, for example, would not be possible or would be deficient. In this article, we try to clarify the basics of what an API is and how you can use it.


  • 05. 04. 2019
  • 4 min read
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What is an API?

As we mentioned earlier, an API comes from the concept Application Programming Interface. Basically, an API is a system of tools and resources within an operating system that allows developers to create and communicate software applications. In terms of programming, an API is what is generally known as an abstraction layer.

If you did not find it clear enough, we’ll explain it more easily: an API is a software that acts as an intermediary between two applications. It is a messenger that helps applications to communicate or to talk to each other.

If we think of an illustrative example of everyday life, you can imagine what happens when you order a pizza over the phone. Before the pizza arrives at your place you must tell the waiter in charge of taking the orders over the phone what kind of pizza you want, right? Then, the waiter will ask the chef (system) to prepare your pizza as you ordered.

Once it is ready, is going to be delivered to your address. In such a situation, the waiter who takes the order over the phone and communicates it to the cook would be an API. Why? Because the waiter is responsible for taking your order to the system to give you back what you are requesting. Just like a real API does when it provides a communication channel for applications and services to talk to each other.

API function

Basic API interconnection

The previous example shows you in a very basic way the function of an API, however, there are several cases in which multiple APIs are used at the same time, for example, when you go booking hotels or airline tickets through travel portals like Kayak, Kiwi or Expedia. All of them connect you to hotels and airlines through different APIs to satisfy your search request.

One more example to finish with our explanation of the functionality of an API is what happens when you decide to request an Uber through Google Maps. When Google Maps asks Uber for information such as travel cost, car availability, location, and other information, the Uber API receives this request, processes the information with the Uber platform and returns the results to Google Maps.

Main publications such as Forbes and Tech Crunch considered 2017 as the year of the API economy.

The language of API

In general, an API uses a language known as JSON (Notation of Javascript Objects). JSON is an open source library based on Javascript that provides methods designed to extract and use data stored in HTML documents. This library is where the REST API calls are located.

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What is a REST API?

A REST API is the evolution of the basic API and is translated as Representational State Transfer. A REST API behaves in a very similar way to a website, that is, the REST API is executed by making a client-to-server call from which the data is returned through an HTTP protocol. Do you remember the example we used with the pizza order? Works just like that.

Therefore, a REST API provides us with functions to use the services of a site or platform on the Internet that is not ours, for example, Twitter or Facebook. We can take as an example the API REST of Twitter and the clients that use it as the case of Tweetbot, Metrotwit or Birdie. When each of these clients uses the Twitter REST API, the methods and functions of the API are limited and cannot be modified, that is, new functions cannot be added. In this way, Twitter can be sure that its REST API will behave according to its default anointing. The same goes for many other online services.

The advantage of using the APIs created by other developers is that you will save a lot of time in creating code for your own applications since you can get many functions encapsulated and successfully tested in the JSON library. Thanks to this, you can dedicate yourself to designing your applications more quickly and efficiently, regardless of the programming language you use. Now you know why APIs are so important to interconnect.

Interesting facts about the APIs

– From 2007 to date, the use of APIs has increased 13x.

– Google and Facebook receive around 5 billion API calls per day, while Twitter receives 13 billion.

– 60% of eBay transactions are made through its REST API.

– Google has more than 200 APIs. The most used Google API is Maps.

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