What is Spring Boot and why is it used for backend development?

Spring Boot is a framework that makes it easy to create production-ready Java applications with minimal configuration.

**Why Spring Boot over plain Spring:**
- **Auto-configuration** — detects what you need and configures it automatically
- **Embedded server** — Tomcat/Jetty built-in, no WAR deployment needed
- **Starter dependencies** — one dependency pulls everything you need
- **Actuator** — built-in health checks and metrics

**Create a REST API in minutes:**
```java
@RestController
public class HelloController {
@GetMapping("/hello")
public String hello() {
return "Hello from Spring Boot!";
}
}
```

**Used by:** Netflix, Amazon, Uber, LinkedIn for microservices

Spring Boot + React is one of the most popular full-stack combinations in enterprise.