I think that one of the reasons it's so hard for people to answer that question is that there are many kinds of love. There is principled love, like love for what's right or even love for one's enemies, for whom a person may not have affection. There is spiritual love, a deep and abiding and reverent love for God or the benevolent affection of God for his creatures. There is romantic love, which when properly expressed is far more dignified than the movies would have you believe, and there is that love, that deep, warm, personal attachment that one has for a freind, or a parent has for a child. There is also that strong, passionate affection one feels for a person that constitutes the emotional incentive to conjugal union; such as the love between husband and wife. There is even an impersonal love, such as when people love gardening, or love a sunset. So it is no wonder, then, that people find it hard to define.
If I had to define love in general in a simple term, I would use the word "devotion". Love attaches itself to someone or something and is unselfish. It is not passive; it actively works for the good of the loved by the one who loves. You often hear people speak of "toxic love". That's not love. That's selfishness masquerading as love. Real love is as rare and as valuable as one's own life. And, like life, it needs to be cultivated and taken care of, because, like life, love can die.
Man, did I ever get serious there for a couple of minutes...