What's the difference between these practitioners?

what is the difference between a general practitioner and a private practitioner

Well, I think that the major difference is that the private one is able to work independently. They do not HAVE to be a part of a managed health organization.

general practitioner vs. specialist

[ the family doctor vs. an endocrinologist]

private practitioner vs. hospital staff member

[your own outside family doctor or endocrinologist who visits you at the hospital during your stay vs. a resident doctor ]