1) You don't care, or you don't know what to do.
2) When you really do care about
something but you don't want to hurt anyone's feelings, or make them
mad or
something.
Boy: "So where do you want to eat?"
Girl: (really wants to eat at "
McDonald's") "It doesn't matter".
Boy: "Alright, LET'S GO TO '
BURGER KING'!!!!"
Girl: (I was hoping that we could go to "McDonald's", but...ah, it's
fine)