Fun fact: they called it "Platonic" love specifically because Plato was like the one Greek philosopher who didn't take advantage of and fuck his students. He took a volcel oath because he was too focused on philosophy, and trying to ignore that asshole Diogenes who kept cramping his style by being right about everything.

what is different between romantic and platonic love? Is it the sexual attraction?

I would clearly say no to that. You can feel romantic love without sexual attraction and sexual attraction without romantic love, it's just that this doesn't work that way for everybody - allosexual people will almost always also sexually desire somebody they are romantically in love with, some demisexual people will not be able to be sexually attracted to somebody they do not also love romantically, but these experiences aren't universal. Romantic, platonic and sexual attraction are seperate desires that can occur together, and they mostly do, it's hard to find relationships built exclusively on one kind of attraction, but they will not always be present in the same amount and mixture in every relationship. There's other types of attraction as well, such as sensual (the desire to be cuddly, tender and physically intimate with somebody), aesthetic (the admiration for the beauty of another person) or even intellectual (it's a fairly central part of many of my relationships to have deep, mentally stimulating discussions and long mutual infodumps with these people, and i quickly grow bored off crushes that can't establish that kind of connection with me) and more, depending on what you need to give and take emotionally. And there's ofc relationships that combine all of those desires, just as there's people who will find fulfillment of some of these desires with one person and fulfillment of other desires with another.

I'd say romantic desire is unique in that it involves a bond that aims to build a mutual future, a shared existence with somebody. To live our lives together, not temporarily like roommates or family members who will at some point part ways to some extend, but indefinitely.