Love is all about whistles.
Ah, guess I should say more.
Love is more than friendship, but it also has its roots in friendship. And that said, I also think that the definition and interpretation of love varies across both cultures and individuals. So I think it's impossible to define clearly what love is. To be fair, it basically is what you say it is. I mean, if you're saying "I love this sandwich" and then say "I love this girl," chances are you're talking about two different forms and/or degrees of love there.
I think of love as a bond between two or more people. When you love another, they're more than just a friend; they're someone you very, very deeply care for. Someone you love can also be someone you could see yourself marrying one day, though that doesn't have to be the case. Love basically just depends on depth, complexity, etc. of the person who is defining it. Like I said, it changes from person to person.
Just take what you think is love, make it, and don't lose sight of it. Its definition is inside you.