What is REST API and how does it work?

REST (Representational State Transfer) is an architectural style for building APIs.

Key principles:
- **Stateless** — each request is independent
- **HTTP methods** — GET (read), POST (create), PUT (update), DELETE (remove)
- **Resources** — everything is a URL endpoint

```
GET /api/users → list users
GET /api/users/1 → get user 1
POST /api/users → create user
PUT /api/users/1 → update user 1
DELETE /api/users/1 → delete user 1
```