Well I'm sort of a hopeless romantic, so for me love is that thing that you watch everyone else use, abuse, and toss aside like pure garbage while you emotionally and mentally starve to death.
Love is simply a chemical reaction that occurs in the brain, a prolonged infatuation if you may, it's just a system that evolution created in human beings in order to preserve the continuity of the species. However, that doesn't make it pointless. Love is the most important thing in human life. It creates inspiration, joy, it produces happiness and can be positive towards your health; it creates a bond to something (not always a person--you can love a subject, an activity, a career, anything) -- a bond almost as strong as the ones that keep our very cells together; it's like infusing your very essence into another being (or subject, career, art, etc.) -- you become one with it. Under this, you could theorise the possibility of love at first sight, your essence meshes with that of this person, the rest is just solidifying the bond (Moulin Rouge comes to mind). However, while this bond is being re-enforced, it is very vulnerable and quite unstable; our emotions and our actions tie in with its progress and can destroy the bond at any time. As the bond grows, it becomes harder and harder to break (think of people that stay in love for years, or when they're still growing, it becomes harder to let go in the end). I think love evolves just as much as we do, it changes just as we do through our lives; it can decay if you allow it to do so; it's not a perfect and permanent thing that lasts forever, it has to be maintained like a beautiful rose garden; roses don't just plant and grow themselves (well they do, but you get my point)!
~Words From A Hopeless Romantic
Edit: I've only been in love once, and it was a far more unique sort of love, so I'm probably dead wrong about everything.
Okay so that's a little overly dramatic, but yeah. I have a video that pretty much sums up love (it's rather offensive so I don't suggest watching it if you're easily offended and can't take jokes):
Love is a many-splendored thing,
It's the April rose that only grows in the early spring,
Love is nature's way of giving a reason to be living,
The golden crown that makes a man a king.
Once on a high and windy hill,
In the morning mist two lovers kissed and the world stood still,
Then your fingers touched my silent heart and taught it how to sing,
Yes, true love's a many-splendored thing.
~Frank Sinatra