What Is a REST API? A Plain-Language Explanation

You’ll see REST API mentioned in almost every job posting and tech article. But what does it actually mean? This guide explains REST in plain language with real examples, so you can both use REST APIs and build your own.

REST in Plain Language

REST (Representational State Transfer) is a set of conventions for designing web APIs. A REST API is simply an API that follows these conventions. It uses HTTP — the same protocol your browser uses — so it works with any programming language and any platform.

The key idea: resources are nouns, HTTP methods are verbs.

• /users is a resource (noun)
• GET /users is “retrieve all users” (verb + noun)
• POST /users is “create a new user”
• DELETE /users/42 is “delete user with ID 42”

The Six REST Constraints

REST has six principles, but the ones you’ll use every day are:

1. Stateless — each request contains all the information needed. The server doesn’t remember previous requests.

2. Uniform interface — predictable URLs and HTTP methods.

3. Client-server — the client (browser/app) and server are separate. The API is the contract between them.

REST API in Practice

Here’s what a blog REST API looks like:

Method	URL	Action
GET	/posts	Get all posts
GET	/posts/5	Get post #5
POST	/posts	Create a new post
PUT	/posts/5	Update post #5
DELETE	/posts/5	Delete post #5

The response is typically JSON:

{
  "id": 5,
  "title": "What Is a REST API?",
  "author": "Kaikobud",
  "published": true
}

What Makes a “Good” REST API?

• Uses the correct HTTP method (don’t use GET to delete things)
• Returns appropriate status codes (201 for created, 404 for not found)
• Has consistent, predictable URL patterns
• Responds with structured JSON
• Versions the API (/api/v1/users) so clients aren’t broken by changes

Conclusion

A REST API is just an HTTP interface for your data, following a consistent set of conventions. Once you understand resources + HTTP methods, you can read any REST API documentation and know roughly how it works before even sending a request. Build one with Flask or FastAPI and you’ll understand it even more deeply.

Read next: Building a REST API with Python and Flask

External resource: REST API Tutorial