Spring Framework is the core of all other Spring IO projects
Of course, Spring Download is based on the Spring Framework, and also provides an extension configuration on a conditional model, in a nutshell.
And I would say that it will not be harmful to use Boot for all your applications and not just rely on the Spring Framework. In any case, I'm not sure if this is enough for your applications to use control inversion. I assume that you are going to use other Enterprise features like Security, MVC, JPA, Hadoop, etc. And Boot allows you to simplify configurations for most of them.
All other useful information you can find on Spring IO