What is love?

I was asked this question by a friend. Interesting. What do you mean when you say you love someone? Lets consider the case of the love between a man and a woman. I had always thought that love was the joy in finding the one person who you have always dreamed of, and longed for in your life. But is that what it is? I was told you love someone because you feel safe with him/her. The feeling that the person will not hurt you. That he/she will take care of you and be there for you when you are in need. The culmination of ultimate trust.

Is it?

What happens when you find out you are wrong?