What is An API
An Application Programming Interface (API) is a contract that allows code to talk to other code. APIs are the building blocks of modern software because they allow for sharing of resources and services across applications, organizations, and devices.
Why are APIs important?
APIs help developers integrate exciting features and build automation without reinventing the wheel
ex: using a Weather API instead of launching your weather balloonsAPIs allow enterprises to **open up their product for faster innovation
**ex: apps that interact with Twitter or Meta APIs by posting on your behalf or reading tweetsAPIs can be products themselves
ex: Software as a Service (SaaS) products like Stripe's payment APIs or Twilio's text messaging and email APIs
APIs - A Digital Restaurant
You can think of APIs as being like a waiter at a restaurant, serving as a go-between for the customer and the kitchen.
A customer who wants soup doesn't go into the kitchen to cook. They don't even have to know how to make soup! They only have to know how to ask the waiter for soup*, expecting the waiter to* bring back soup*.
*APIs work the same way, but there are different names for the players involved. Instead of soup, the requester might ask for data or execution of a service.
| Networking term | Description | Restaurant analogy |
| Client | The requester. Ex: browser, web app, mobile app | Customer |
| API | Simplified interface for interacting with the backend | Waiter |
| Server | The backend where the processing happens | Kitchen |
Types of APIs
Medium
While this course will focus on Web APIs, it is important to know that "API" can apply to a broad range of interfaces.
Hardware APIs
Interface for software to talk to hardware.
Example: How your phone's camera talks to the operating system.**Software Library APIs
**Interface for directly consuming code from another code base.
*Example: Using methods from a library you import into your application.**Web APIs
**Interface for communicating across code bases over a network.
Example: Fetching current stock prices from a finance API over the internet.
Multiple API types may be used to achieve a task. For example, uploading a photo to Instagram makes use of various APIs:
Hardware API for the app to talk to your camera
Software library API for the image to be processed with filters
Web API for sending your image to Instagram's servers so your friends can like it!
Architectures
There is more than one way to build and consume APIs. Some architecture types you may come across are:
REST (Representational State Transfer)
GraphQL
WebSockets
webhooks
SOAP (Simple Object Access Protocol)
gRPC (Google Remote Procedure Call)
MQTT (MQ Telemetry Transport)
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