For me the second question is easy to answer...
A sunny day
And of course there is love in its most common meaning - between male and female. The last one is easy - it is lust. It is sex. It is an instinct for reproduction. Nothing more. People tend to romanticize it, but it's still the same thing that drive animals of opposite sex together. There can also be respect, friendship, common views and interests, but it has nothing to do with love, because love itself is just a physical thing. And nobody will ever convince me of the opposite.
As for original question: I kinda understand what aloneindekalb is asking. He says: love is when your spirit gets excited. I disagree. Thus, my answer: if we are talking about love between friends - yes. If you have common interests and views of life, it is very important for friendships, they are actually based on it.
If we are talking about love between man and woman - no. Love is when your private parts get excited. If you don't want to have sex with your partner - there is no love. There is just friendship. And it's a totally different ball game.
In my opinion, man and woman shouldn't base their relationship/marriage just on friendship, as it's a different type of love, which follows its own rules and instincts, and also often falls apart.