Can you even explain more deeper than just FRIENDS?

"FRIEND" What does this word mean? What does it actually mean? Can you even explain more deeper than just Friends? Or could it be more?

"Expect the unexpected" When you just don't expect this kinda things to happen, for some reason, it just happened and when it happen, you have no way of turning back. You wish to have the emergency STOP button for you to press, but somehow you just cannot stop it.

My Story: Once upon a time, you know a friend whom you have know him for quite a long time. We were friends, eventually just talking buddy that you can just say hi and bye and a few chit chatting that just to catch up with your friend. Then somehow, you guys became close after some hanging out, and your "friend" had the feeling that is more than "just a friend". But for you, you just have the feeling that he is just a normal nice friend that you like to hang out with and have fun with, nothing more than that.

So, what should you do when you found out that he likes you more than just a friend? Will you feel awkward after he told you? but that is not the important part. The most important part of this is,
What would you react to it when you know, and after knowing it, will you have a distance to him?
Or you continue to act normal like it never happen?
Is it cruel to ignore?
What can i do about it?
Avoid him is not the solution...
Do you think it's rational to be still friends with him as for he is still having that feeling for you?