What is REST?

REST (Representational State Transfer) is an architectural style for building networked applications and APIs that describes how a client and a server should interact over HTTP.

In simple terms: REST is a set of principles that make building an API convenient and clear.

---

#What matters to understand right away

REST is not a protocol and not a technology. It is a set of rules and approaches that are usually implemented on top of HTTP.

---

#The core idea of REST

REST is built around resources.

• a resource is an object or entity (a user, an order, a product)
• a resource has a URL
• actions are performed on a resource through HTTP methods

Example:

• /users/1 - a user
• GET - retrieve
• POST - create
• PUT / PATCH - update
• DELETE - delete

---

#The main principles of REST (in plain terms)

#1. Client-server

• the client and server are separated
• the client is responsible for the interface
• the server is responsible for data and logic

They can be developed independently.

---

#2. Stateless

• the server does not store the client's state
• each request contains all the needed information

We already covered this, it is a key principle of REST.

---

#3. Resources and URLs

• everything is a resource
• each resource has a unique URL
• the URL describes what, not how

/getUser?id=1 is bad /users/1 is good

---

#4. Using HTTP methods as intended

• GET - retrieve
• POST - create
• PUT - replace
• PATCH - update
• DELETE - delete

This makes the API predictable.

---

#5. Using HTTP statuses

• 200 - success
• 404 - not found
• 401 - no access
• 500 - server error

The client understands the result without parsing text.

---

#6. Uniform interface

• the same rules for all resources
• the same response formats (often JSON)

The API is easier to learn and use.

---

#REST in practice (an example)

Request:

GET /users/1

Response:

Clear even without documentation:

• what we're doing
• with what
• what the result is

---

#REST ≠ REST API (a common mistake)

• REST is an architectural style
• REST API is an API built according to REST's principles

Most "REST APIs" in practice are REST-like, but that is enough.

---

#Real-life example

REST is like a store with rules:

• the address is where the item is
• the method is what you want to do
• the response is the result (success or an error)

Everyone knows the rules, there is no confusion.

---

#Short answer for an interview

Remember this wording:

REST is an architectural style for client-server application interaction, based on working with resources over HTTP, using standard methods, a stateless approach, and HTTP response codes.