The second class-level annotation is `@SpringBootApplication`.
This annotation is known as a _meta-annotation_, it combines `@SpringBootConfiguration`, `@EnableAutoConfiguration` and `@ComponentScan`.
Of those, the annotation we're most interested in here is `@EnableAutoConfiguration`.
`@EnableAutoConfiguration` tells Spring Boot to "`guess`" how you want to configure Spring, based on the jar dependencies that you have added.
Since `spring-boot-starter-web` added Tomcat and Spring MVC, the auto-configuration assumes that you are developing a web application and sets up Spring accordingly.