I see the difference between the two as Community Chat being about anything you want (and doesn't have its own forum, like Beauty, Fashion, etc. has).
I see Q Talk as being about QVC as a company, such as their hosts, their policies, the programing, their pricing, brands, etc., although I see many people using it as a place to discuss anything they want.
Never heard what the original intent was, but that is how I use these two forums when I want to start a thread.