Friend : Friend is there with you in all time. Will support you when you need it & he/she is the only one who is on your way only when you are going down, tell you when your face is dirty... basically support you when you need it but at the same time stops you going in wrong direction....
Basic difference in my opinion just friendliness may turn out to be very harmful sometimes if other person may count on him/her and may get nothing other than disappointment or may be in some problem... Just my POV.