Share 'What Determines a Hole in the Wall??'

So.....the question has come up and I think it needs its own discussion....What exactly in your opinion constitutes a Hole in the Wall?? Does it have to be cheap or can it be upscale, too?? Is it totally off the menu, a buffet, or no menu at all?? What is the difference between a small independent restaurant and a hole in the wall?? Does the type and quality of food matter or is it simply ambianc…