What Is a REST API? And Why Does Everyone Use It?

You have been building automations and apps with Claude, ChatGPT, Cursor, or Bolt, and you have heard the word “API” explained before. But then someone mentioned a “REST API” specifically, or your AI wrote code that called a “RESTful endpoint,” and you realised you did not know what the REST part meant. Is it different from a regular API? Do you need to care about it? Here is the clear explanation that most tutorials skip.

Quick Recap: What an API Is

An API is a way for two pieces of software to talk to each other. When your script fetches data from Shopify, sends a message through Slack, or checks the weather, it is using an API. The API is the agreed-upon way of making those requests and receiving responses.

If you want a fuller explanation, the API post earlier in this series covers it in detail. For this post, the important thing is that APIs come in different styles, and REST is by far the most common one.

What REST Actually Means

REST stands for Representational State Transfer. That name tells you almost nothing useful. Here is what it actually means.

REST is a set of conventions for how APIs should be structured. When an API follows REST conventions, it is called a REST API or RESTful API. The conventions cover things like how URLs are structured, how requests are formatted, and how responses come back.

A one-sentence definition: a REST API is an API that follows a standard set of conventions for how to request and receive data, making it predictable and consistent to use.

The reason REST became the dominant standard is simple: consistency. When you know an API is RESTful, you can predict how it works before reading its documentation. The patterns are familiar.

The Key REST Conventions You Will Encounter

REST APIs use standard HTTP methods to indicate what you want to do:

GET means retrieve something. When your script fetches a list of orders from Shopify, it makes a GET request.

POST means create something. When your script creates a new record, sends a message, or submits data, it makes a POST request.

PUT or PATCH means update something. When your script modifies an existing record, it makes a PUT or PATCH request.

DELETE means remove something.

REST APIs also structure their URLs around resources, which are the things the API manages. A Shopify API URL might look like:

GET  /orders          (get all orders)
GET  /orders/1042     (get order 1042 specifically)
POST /orders          (create a new order)

The URL describes the thing. The HTTP method describes the action. Together they form a predictable, consistent system.

How This Affects You as a Vibe Coder

In practice, you rarely need to think about whether an API is RESTful. Your AI knows which methods to use for which actions and writes the code accordingly. When you ask ChatGPT or Claude to “fetch my orders from Shopify” or “create a new record in my database,” it automatically writes the correct GET or POST request.

Where this becomes useful is debugging. When your script fails, understanding that a 404 error means “the URL you requested does not exist” or a 401 error means “you are not authenticated” helps you diagnose the problem faster.

If you see an error from an API call and want to understand it, ask your AI: “My script got this response from the API: [paste the error]. What does it mean and how do I fix it?”

REST vs GraphQL: Do You Need to Know the Difference?

You may also encounter GraphQL, which is an alternative to REST used by some modern APIs like GitHub’s v4 API and Shopify’s newer API. GraphQL lets you request exactly the data you need in a single request rather than making multiple REST calls.

For most vibe coders, you do not need to choose between them. Your AI will use whichever approach the service you are connecting to requires. If a service uses GraphQL, your AI will write GraphQL queries. If it uses REST, your AI will write REST calls. The underlying pattern is different but the process of asking your AI to write the code is identical.

The One Thing to Remember

A REST API is an API that follows a standard set of conventions using HTTP methods like GET, POST, PUT, and DELETE to perform actions on resources. It is the most common type of API in the world. When your AI connects to external services, it almost always uses REST. Understanding the HTTP methods helps you interpret error messages when things go wrong.

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New here? These might help: What is an API? The honest explanation nobody bothers to give you. → What is an SDK? And why does your AI keep mentioning one? →