Student or Learner
When some one ask me 'what's up?'....how do i answer it?
It can mean "How are you?" so you can answer it as if that were the question.
It can mean "What are you doing?" or "What are you up to?"
It can also mean "What's wrong?" or "What's the problem?" If you found someone crying or looking very upset, you might say "What's up?" and they would tell you why they're upset.