What is an API?

Before calling any external API in a tutorial, let’s take a quick step back and understand what an API actually is.

An API (Application Programming Interface) is a way for two programs to talk to each other. Think of it as a bridge that allows two different pieces of software to communicate — often that means your code (running in the browser or on a server) talking to an external service over the internet.

Think of it like placing an order at a restaurant: you (the client) tell the waiter (the API) what you want, and the waiter brings it from the kitchen (the server). You don’t need to know how the kitchen works — just how to place an order properly.

HTTP methods

Most APIs you’ll work with are REST APIs, which are the standard way web applications communicate over the internet. They use HTTP methods — the same methods your browser uses to fetch web pages. The two most common are:

• GET — when you want to retrieve data from a source (like reading a webpage).
• POST — when you want to send new data to a source (like submitting a login form).

There are also PUT and DELETE, which you’ll meet in tutorials that update or remove data.

A real-world example

Imagine you want to build a Pokémon Information App.

The hard way to build this app would be manually researching and typing out the stats for all 1,000+ Pokémon into your own database. This is where an API saves the day. There is a free service called PokeAPI that already has all this data. You just have to ask for it!

Here is how the interaction works:

1. The Request: You send an HTTP request to the API asking for specific data (e.g., “Give me the stats for Pikachu”).
2. The Processing: The API server receives your request, finds Pikachu’s data in its database, and formats it.
3. The Response: The server sends the data back to you in a format your code can read, usually JSON (JavaScript Object Notation).

In code, making that request looks like this:

const response = await fetch('https://pokeapi.co/api/v2/pokemon/pikachu');
const apiData = await response.json();

And the apiData you get back will look something like this:

{
 "name": "pikachu",
 "height": 4,
 "weight": 60,
 "types": [
   { "type": { "name": "electric" } }
 ]
}

QUESTION: Looking at the JSON data above, how is a JSON object similar to a standard JavaScript object? If you wanted to get the Pokemon’s weight from apiData, what code would you write?

After you get this information back, you can parse it and use it however you’d like.

If you want a deeper visual explanation, check out this 3-minute video on APIs.

Helpful videos

• What is an API? (by Simply Explained) This video explains APIs using real-world analogies — perfect if you’re just starting out.

• 4 Most Important HTTP Requests That Can Be Made to an API This breaks down the core HTTP methods you’ll use when working with APIs: GET, POST, PUT, and DELETE.

What is an API key?

An API key is like a password that allows your project to communicate with a third-party service. It tells the API who you are and whether you’re allowed to use it.

Think of it like a secret access badge — you’ll need one to send requests and get a response back from the service.

Because an API key acts as a password, it must never be committed to your repository. See Environment Variables & Secret Safety for how to keep it out of version control.