Definition of Managed, Referenced, Used

What are the definitions and meaning of the terms of Managed, Referenced, Used?

I realize this should probably be addressed somewhere in core. I've read various pieces of documentation on the meaning and use of the terms Managed, Referenced, and Used. But it is still not entirely clear to me what these terms are intended to mean or track. Since this module does an excellent job of reporting on these various states, I was hoping I would be able to get a better understanding of them by using the module. But simply saying it is or is not in the usage table or managed table doesn't help me with context.

Can someone define three distinct terms, explain why they exist, and what their significance is? What are the intended uses and meanings of these terms? If a file is referenced does that mean Drupal thinks it is linked to from somewhere in the site content? If a file is used, does it mean it was uploaded via a file field or via a module like IMCE? If a file is managed, does it mean it's in the database?

Thanks!