What a question!
Some might say that love is a chemical reaction in the brain and body, nothing more. Of course anybody who has loved another--be it a parent, spouse, child, or friend--knows that love is something more. And anybody that has ever loved another with no hope of gaining anything knows that there is no logical reason for love to be reduced to something of an instinctual biological reaction.
In addition, our society uses love to extreme degrees. One can say, "I love dark chocolate" and in the next breath say, "I love his wife." To a teenage girl headed to junior prom, love means something substantially different than to the 85-year-old man standing beside the grave of his wife of 63 years.
Love is an interesting gift. It is spectacular and special. It connects us to one another in ways often unexplainable. There is nothing else in the world like love, which should not come as a surprise considering that John tells us that not only is love from God (1 John 7) but that God is himself love (1 John 8). In addition, Jesus taught his disciples that there is no greater love than one who lays his life down for his friends (John 15:13).
Love is complex and for many, this answer will not suffice. Too often people have a picture of love as some kind of euphoric feeling they get from having that one and only special someone in their lives. But this picture is not really correct because it's selfish. This picture of love is about a person wanting to be loved and getting something from it. No, love is something more. It's not selfish and it's not about getting. Love is an action word. It is a relationship. I've even heard it said that love is a verb. So no matter how people try to explain love, I find it's best to turn to the Bible because where we see Jesus (in any book of the Bible), love will always be nearby.
*Photo by Stephen Poff is registered under a creative commons license.