SharePoint 2010 Services and Features

I've got several general questions related to the SharePoint 2010:

1. Which Farm enabled features offer which Web Application features?
2. Which enabled Web Application features offer which Site Collection features?
3. Does exist a one-to-one relation between Farm Features, Web Features and Site Collection Features?
4. Is there an overview of what Farm level Application services offer what features?

Thank you in advance for your help!

Mihai