I tried to find an answer to this question. But no luck. Can somebody explain it to me? An American friend of mine said, "I've never heard about 'What does it mean?', I've always used 'What does that mean?'". My other English friend said: "It depends on context." I asked, what context? He tried to explain but couldn't. So now I'm asking you:
What is the difference between "What does it mean?" and "What does that mean?" in common speech?