"What is the difference between a good question and a bad
   question?" It depends on who is answering. Usually it's a "bad
   question" when someone can't answer it without calling it a bad
   question first.

   When I call something a bad question, I sometimes try to rewrite
   it a few different ways, or substitute other words and answer a
   question that I *can* answer. Or if I'm really stuck, I'll ask
   it to be rephrased.

   It's a "good question" when they *can* answer it - or it makes
   them pause and they take a moment to think and reflect.