Definition of a Good friend

What is it? Is there a clear distinction between a good friend and a boy friend? I used to think there is, and still believe that there is. But does everyone knows how to distinguish between the two?

How close is not too close? How intimate is not too intimate? Would you be uncomfortable if a good friend is being too nice to you? Would you feel intimidated by a good friend being too concern about you? Would you be irritated by a good friend's intermittent calls and care?

If I were to answer all those questions, I would say NO. And it is damn obvious that I think NO.