if you work in Tech or in anything adjacent to tech, you've probably heard the abbreviation API being thrown around, so let's talk about APIs. What are they and why do we need them? Let's start with what is an API. API stands for application programming interface. Fancy words, so let's break it

down. Application in this context just means any software that has a specific functionality or purpose. Interface refers to a contract or a protocol that dictates how two applications talk to each other using requests and responses. So put together, an API is simply a way for different systems or applications to

communicate with each other. Okay, cool in theory. So why do we need APIs? Let's start with a non-technical analogy first. Let's say you have a dinner reservation for tonight for three people, but you want to change it to six because some friends decided to join you at the last

minute. So you call the restaurant, ask them if it's possible to do that, and the customer service person puts you on hold. It takes a minute, but they finally come back and they say yes. Simple. You called someone, made a request, and you got a response, yes or no. Now let's say that

there was no customer service person and that it was up to you to figure out how many people have made reservations for the same time at this restaurant, how many tables do they have free at that time, what's their kitchen capacity, what's their wait staff capacity, all

to figure out whether you can add three more people to your reservation. That's a lot of unnecessary work on your part, work that you, the customer, have no expertise in and it means that the restaurant has to reveal a lot of data to you, maybe even private data about

who's eating there that night and who works there, etc. In this analogy, the restaurant is an application that provides a specific service or function, which is to feed you. You are an application that is trying to get fed with a group of friends. The customer service rep from the

restaurant is the restaurant's API, that is the interface through which you can communicate with the restaurant and make requests like changing the number on a reservation, and you can do that without having to dive into the messy details about how restaurant reservations work or anything like that.

For a more technical example now, think about Apple's weather app. Do we think that Apple decided to set up weather monitoring stations around the world? That's a really expensive endeavor, and if it was super critical to Apple's business model, then maybe sure, we could

we could see that happening. But there are already services out there that meticulously collect global weather data, services like weather.com. So if weather.com creates an API through which anybody can access their data, but only in the ways that weather.com allows, then Apple could just use that API to

populate their weather app. So how do APIs actually work? Let's use the example of web APIs, which are the type of APIs that deliver client requests and return responses via JSON or XML, usually over the internet. Each request and response cycle is an API call. A request typically consists of

a server endpoint URL and a request method, usually through HTTP or hypertext transfer protocol. The request method indicates the desired API action. The HTTP response contains a status code, a header, and a response body. The response body varies depending on the request, and it could be the server resource, a client

needs to access or any application-specific messages. One status code you might be familiar with when you've tried to visit a website that might be down or doesn't exist anymore is the error 404 code: URL not found. And that's it for request/response. To get more in-depth about APIs

and the various different types that exist, I encourage you to check out the Exponent article linked in the description below. Good luck with your interviews and thanks for watching. Thank you.

APIs Explained (in 4 Minutes)

Exponent

API stands for Application Programming Interface; it's a way for different applications to communicate.

An application is any software with a specific function, and the interface is a protocol dictating how applications communicate using requests and responses.

Analogy: changing a dinner reservation - using a customer service rep (API) is simpler than figuring out restaurant capacity yourself.

The restaurant is an application, you are an application, and the customer service rep is the API.

Example: Apple's weather app uses weather.com's API instead of creating its own weather monitoring system.

Web APIs use JSON or XML over the internet; each request/response is an API call.

A request includes a server endpoint URL and a request method (usually HTTP).  The response contains a status code, header, and response body.

Example of a status code: Error 404 (URL not found).

More in-depth information on APIs and their types can be found in the linked Exponent article.