I have always believed that if you have one true friend in your life, then you should consider yourself very fortunate. Just like anything else, individual people are going to have different ideas about what it means to have or be a friend. I recently was in a situation where I thought I had a pretty close friendship with someone, only to realize that I didn't know that person AT ALL! Did I also mention that you should never assume anything, either? That includes friendship. Sometimes you find out how people really feel about you in the strangest, most unexpected ways.
I was having a conversation with someone, and that person happened to mention that my "friend" would use going somewhere with me as an excuse to her husband so she could go out with another man. I must have looked as stunned as I felt because they immediately tried to change the subject. I was stunned. I thought we were friends. We had some very deep, personal discussions and shared private information. I don't appreciate being dragged into someone's affairs without my knowledge. If you're unhappily married, I suggest you leave. I stayed silent about it until I realized exactly how two-faced the person actually is.
A situation came up. She and a lot of other people had an awful lot to say about it behind the person's back. She actually made a very racist remark about a person and why they had low self-esteem, and then attempted to gloss over it and make it like she never said anything, and that should never fly. You want to say it. You better OWN IT.
Friendship to me is pretty simple. It's someone who likes and cares about you, flaws and all. They have your back just like you have theirs. Sounds simple, doesn't it? Yet it is as elusive as Bigfoot. I learned my lesson.