My Dilemma

Sorry it's been so long since I posted, but I really haven't been able to come up with anything insightful or interesting, and I don't think this post will break that streak, but here is something I don't understand: love.

What is it? An emotion? A scientific reaction? A spiritual connection between two people? Why is it so hard describe? And why are there only certain people who make you feel it? Why will people give up their lives for the ones they love? Has it always existed? Do any animals other than humans feel it in the same way? What is love without all the romanticized connotations attached to it nowadays? Is it more than friendship even if you take away the sex? What makes love toward family different than love toward a husband or wife? Boyfriend or girlfriend? How can you love more than one person at once? How can you fall in and out of love? Or rather that seems to be more understandable, so how can you love one person for your whole life? When did marriage become based on love?

I seriously don't even have any hypotheses to answer these questions. I'm just getting to that point where I'm honestly curious for some answers, not having had much time in my life to gain experience in the love area.