it means that someone is telling you something you want to hear and flatters you/plays with your heart strings, but has no real intentions of being with you or loving you.
like if you're dating this douchebag who cheats on you all the time and he tells you sweetly "baby, I love you. you're beautiful to me and I'll change for you...'' and blah, blah, blah, but he has no intention of changing and probably doesn't love you at all.
it's using romantic language to manipulate someone's emotions.
hope that made sense, haha