What This Topic Established

A starter declares no code of its own, only a curated, version-matched list of other dependencies. spring-boot-starter-web resolves to Spring MVC, Jackson, and an embedded Tomcat — verified against a real dependency tree.

The server lives inside the jar, so java -jar alone is enough to start listening on a port. Swapping it — to Jetty, for instance — means excluding the starter's default server and adding the one you want instead.