What is love

Love is an attractive force between the lover and the loved. It reminds me of qi the sense that a lot of people think of it as having only one sensation. In fact, there are different types, and each type feels differently. The lowest love only attracts/pulls you to your own desires; the highest is so strong that it pulls you out of yourself and you're not even on your own mind.

Things that come to mind with the word love...

Unity (One-ness)
Gravity (a force of unity)
Harmony (Flow without resistance that promotes gravity)
Acceptance (resolve within the self to diminish self-resistance to promote harmony)
Faith (trust that things are just as they need to be to promote acceptance)

Notice how they all word toward Unity as the nature of reality.

The Greeks defined four types of love:

Storge: this is the protective, nurturing love that family members tend to feel for each other, especially parents for their children.

Philos: this is the love one feels for a friend (non-romantic).

Eros: this is the romantic, pationate love that is shared by lovers. It entails sexual attraction, the need to "possess".

Agape: a universal love, usually equated with compassion. It sees beyond what is and accepts the whole.

I believe that all love is rooted in a deep empathy born out of the knowledge (whether conscious or not) that we are all one, as Streen said. When you feel this interconnectedness, you "see" yourself in the other person, and can feel love (agape) for anyone, because you ultimately see beyond the person and realize that you are reflected in them, their struggles, their imperfections, you can relate to them as your own.