If you say, "Bye!" you mean "farewell" or "so long." In other words, bye is a shorter way to say, "Goodbye."

Does goodbye mean forever?

Goodbye is only for people you are never going to see again. When you are used to people saying goodbye and leaving you, it can be difficult to have hope that not everyone is going to do the same. Saying "see you later" is sort of a consolation, a promise that they are not going to leave–that this is not forever.

Is bye the same as goodbye?

There is a subtle yet simple difference between "bye" and "goodbye" in English. You say "bye" when you are leaving and you will see the person again. "Goodbye," however, is often understood as an indefinite parting, that it may be the last time you will see the person again.