When a girl loves a guy, she becomes fucking obsessed with him. She wants to spend every waking minute with him and gets all pouty & emotional whenever he goes out with friends but doesn't bring her. During the week when he's getting his shit done, she'll flood his phone with texts begging him to come over and fuck her. When they go out together, she'll follow her man around, get incredibly jealous when he does something as innocent as simply acknowledging a female acquaintance who he happened to run into, and most importantly, she'll treat every other guy as either a weirdo or a clown who's purpose is to entertain her.
When a guy loves a girl, he legitimately wants to hang out with her when they go out together, he is able to socialize with her without thinking about or even caring about having sex with her later, he feels comfortable (even when he doesn't prefer it) having her around when he's shooting the shit with his guy friends, he legitimately wants to have sex with her more than any other girl because he feels a physical connection (a sort of sexual *flow) with her that he can't put into words, and he treats all other girls as insignificant attention seekers who are a huge waste of his time, genuinely uninteresting people, and philanderers who ignore all the single guys competing for their attention but are willing to throw themselves at him for no other reason than "he's taken" and therefore poses a challenge. Women want what they can't have, and when they know that a man is genuinely in love with a woman, they're all to willing to make it blatantly obvious that if he wants to cheat on his girl with them, he has that option whenever he damn well pleases.
This is how I view love based on the past relationships in which I've genuinely felt it within me as well as genuinely felt it from my partner. It's rare and doesn't last very long unless your game is bulletproof.