Love, as everything else, is subjective.
For me, it's a good guy that I've been friends with for a time, someone who listens and is funny and intelligent. Not very perverted, hopefully, and enjoys gaming and reading.
When falling for someone, falling in love, for me, it's just a "bang, wait, I think I like him." But that only happens after I know him. I only even think someone is attractive when I love them.
Love is...a feeling that you can be around someone and enjoy being with them and be able to talk and laugh and care about what happens to them. That's the same in any relationship, family, friends, or romantic. But when it comes to a romantic relationship, there's a little more of a feeling, you think they're attractive and might like being near them even more. Care about them and know that they're a good person and even if you'll fight sometimes, you'll still love them because it's a deep feeling. It's difficult to explain, of course, but so is everything else in life.