Happy Mother's Day (US and Canada) CC

I just wanted to wish everyone a happy mother's day. I hope everyone can get to chat with that person in their lives that has played the role of "mom".

So to make this a little controversial, what is a "mom" to you? What separates a mom from a dad? What is the essence of a mother? Please keep in mind that not everyone was raised by a birth mother, and that there are several times in people's lives where men take on the role of "mom" (which is why I'm asking how is it different from a dad). Please be kind and respectful of other's and I hope we can have an interesting discussion.