What do people mean when they say a parent is a "friend"?

This is always used negatively. But I am not exactly sure what is meant by this when it is used. People seem to act like your parents were either your friends (bad parents) or they were not (good parents).

To me, it always meant that a parent is trying too hard to be a friend to their child in that they are afraid to contradict their child or upset them, so they always give in and are afraid to exact any kind of authority or discipline. That would be the correct usage of the term, correct?

But then I hear things like “a parent should never ever be a friend!”. So, when my mom and I went to open houses together and had friendly conversations, that was her being a bad parent? My parents were never afraid to exact authority over me or discipline, but they were/are like friends to me in many ways.

And there’s all that about how parents shouldn’t ever be “cool”. Well, my parents were pretty darn cool. Kids at school knew them and thought they were cool. Is that such a bad thing? Really I think people are thinking of something else when they say that…

Were your parents ever friends to you? Did you ever think they were “cool”? Did they take it too far to the negative side? How do you use these phrases and terms?