Meaning
A wide happy grin with two red hearts in place of the eyes. This is infatuation in emoji form: being smitten with a person, obsessed with a new outfit, or blown away by a gorgeous view or dish.
It leans toward excitement and desire more than quiet affection: “Just saw the photos from your wedding, the dress 😍” People use it freely for things, not only people, so it is not automatically romantic. Still, sent alone in reply to someone’s selfie, it can read as a crush, which may or may not be the message you want.