Hey dude, we're bestfriends right? :)

I never really call anyone in my life "Best Friend". I mean define "Best Friend". What's that? The higher level after "Friend"?I have a lot of Friends and I love them, so much! They mean so many things for me, more than family in some cases. They cheer me up, comfort me, support me, share me a lot of things, and I believe they love me too.But "Best Friend"? Give me a reason why do I have to call