Most Helpful Guy
It means you're ready to communicate. It's like the re-establishment of diplomatic relations between countries. It's an improvement of very poor relationships where people do not even want to hear each other to when they're ready to communicate again. There is less hate. But the mutual attitude is most likely passed from almost enemy to hostile/very unfriendly.
Most Helpful Girl
It usually means they made a hasty decision when they blocked you Probably because the person was angry or hurt so made a rash decision. Unlocking someone means you regret blocking them , and it does usually mean you are opening the way back up to communicating with that person again.