Two of them exist in our daily life. However, ideal friends exist in people's mind. They should be diligent, successful and loyal. When you need help, they will stand beside you and be delighted to give you a hand. Also you can share your happiness and sorrow together.
In my opinion, friends can share something but they also should keep their own secrets. So I wish my friends wouldn't interfere in my privacy too much. On the other hand, my friends should have Something in common with me, at the same time something special. In this way we can attract each other and learn from each other.