When given a very specific question that you know has a very specific answer, your first reaction might be to blurt out the answer and be done with it. However, I like to go the extra step and ask what they've tried so far or what research they've done. I like to show them how to arrive at the answer on their own as well as provide the solution.
He suggests that it's more about the thinking behind the answer than just reciting something from memory. Anyone can memorize facts and terms (and solutions, for that matter) but a good developer will be able to explain why he came to that conclusion.