Questions on component development and the tutorial

[wfr2000]

Greg,

I appreciate your tutorial. Could you answer the following questions (and possibly include the answers in your tutorial, too):
Where does admin/services/provider.php come from? It seems to be necessary for the component to work.
Could you comment the contents of this file?
Where is it being called?
Where ist admin/src/Controller/DisplayController.php being called?
Is DisplayController.php the entry point into the component?
Don't we need an admin/helloworld.php file?

Thanks.