"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.