No idea. I'll get back to you when someone tells me I've experienced it.
Just Kidding. Love is a really strange emotion, or maybe even a set of emotions, I find it hard to categorise. It's often split into many different forms that are applied with different people and/or situations, so I don't think there is any all over all round definition for what "Love" is. I think it does end up coming down to being a personal thing.
How do you tell that you're in love? For me, when I first experienced it, or assumed I did (Can we actually tell?) it was a combination of physical and emotional responses to whenever I spent time with a particular person that I had never before felt and therefore assumed that this must be love. After a fruitful year and a half long relationship I realised that this initial combination or cocktail of feelings had almost entirely dissipated, and that I was pretty much in the relationship for the sex and good friendship we shared. So, we broke up, but continued to be extremely good friends and even messed around sexually every now and again until he engaged in another committed relationship.
I suppose that love for me is going to be a recreation of those conditions I originally listed when I first believed that I had fallen in love.
On this subject, I don't think love is a set of emotions limited to one person alone, and that more people may fill places in your life and you can feel love for them. I suppose that means I am a supporter of open relationships, but only if everyone in this group of lovers is entirely comfortable with the principle. Being bisexual, and having messed around with both guys and girls sexually for fun, I don't actually care if my partner(s) sleep around as long as they still love me. If they don't, just tell it to my face rather than hide it. As long as our love is still there, meh, they can do what they want, I'm not going to hold them back, and if I find we no longer love each other, then simply part ways, hopefully as friends.
So yeah, take it how you will. *Prepares a lot of anti-flak shielding*