I have a friend, a boy. He always saying that he likes me. But nothing else. Just saying. I want to know what he really wants from a boy's opinion. Why did he always say it? Can anyone help me?

There is no way to know what HE wants .. Or intends. No one, wether it be boy or girl, can accurately know what HE is thinking.  He 'may' have the courage to say the words that he likes you, but not the courage to persue it .. He may just consider this as a way of being friendly .. No one knows but him.  The only way to know is to get to know him better, and it will all be revealed to you.