We now have a very humble spring web application with a RESTful JSON "Hello world" despite having configured nothing ourselves. We have seen what spring boot does for us, how it does it, and hopefully we've got a good idea of how to override the default autoconfiguration.
Detailing how spring boot works is the topic of a book all by itself. If you want to dig deeper, I recommend that you read the excellent book Learning Spring Boot by Greg Turnquist in the same collection.
We are now ready for the next chapter where our application will reach a new stage by actually serving web pages, and you will learn more about spring MVC's philosophy.