How do you say what do you mean and what are you talking about in korean?

Question

Answer

What do you mean? 무슨 뜻인가요? / 무슨 뜻으로 말하는 건가요?
What are you talking about? 무엇에 대해 말하고 있어요?

Answer

"What do you mean" = 
formal way(with a friend) = 무었을 의미하는 거야?
polite way(just in case the person you are talking to is older than you) = "무었을 의미하는 건가요?"
"What are you talking about" =
formal way = 무었에 대해 얘기하고 있어?
polite way = 무었에 관해 얘기하고 있나요?