This is what I have told my kids... In life you have a few good friends and lots of "friendlys." Friends are the people who, like someone else said, are almost like family. "Friendlys" are people who you enjoy, maybe even hang out or whatever, but you don't have the connection to them that you do your friends. They might be more then an aquatience, but not as close as a real friend.
It is funny that my DH and I were just talking about this last night. He has 230 "friends" on FB. When he goes on he posts a joke, or something interesting her read or whatever. Nothing about his real life. I have like 30 "friends" on FB. They are all "friendlys" and while I do talk about life sometimes, like the kids or whatever, they are all other moms (and a couple dads) who are good to bounce ideas off of and stuff. But I see myself as having one truly best friend, my DH and a few ery close friends and the rest are nice people who could at some point become better friends but aren't there yet. DH said he has 2 close friends, me as his best and another who is like his brother.
ETA- I had one of those life learning moments as well. When DD9 was an infant she was very sick. I had been up with her for days and had been back and forth to the doctor. We went in on a Friday and he told me if she got any worse overnight to go right to the ER. (She had RSV.) Anyway, I was so tired after a long week and my DH had the weekend off so he told me to get some sleep. He took her to the ER in the night. I woke up to a note and called and she had been admitted. DH had taken the family van and left his 2 seater car. I had 2 kids who were 8 and 3 at the time. I called a "friend" who lives around the corner and asked her to come sit with the kids so I could run there to be with her and DH would come right home. First she said no, she didn't want to catch anything, then I said I'd be OK with her kust sitting in her car outside in case the kids needed her. Then she said it was too early and too cold out. Both of which it was but my baby was in the hospital, you'd think a friend would be running over to help out, I would have for her (in fact not long before that I had driven her and her son to the ER when she didn't have a car.) Anyway, it was a shock, and I didn't call anyone else cause I felt so embarassed by her response. I put both my girls in one seatbelt and took all back roads to the hospital. DH took them home in the van and I stayed for the next 5 days in the hospital with my baby. I never thought of our "friendship" the same. We chat, our kids play, but I will never confide in her or count on her, that is for sure. A few years later I got very sick and wound up in he ER. I found out I needed surgery and was scared to be alone. DH called a different friend to watch the kids and in a heartbeat hey took them so he could be with me overnight and as long as we needed. When they came home, they were happy, healthy and fed and even all their laundry was washed...that's a friend!!!