Perhaps means about the same thing as maybe: things that perhaps could happen might happen, or they might not.
When someone asks if you want to do something and you say "Perhaps" — you haven't committed. It's another way of saying "I don't know" or "It's possible. Who knows?" People use perhaps when talking about things they aren't sure about, or things they don't want to answer in a decisive way. When a friend says, "Perhaps we'll go to that movie," don't count on it. He's keeping his options open.