Bianca is enjoying her senior year of high school in the suburbs of Atlanta, Georgia, with her two best friends, Jess and Casey, both of whom are significantly more popular than she is. She is also the neighbor and former childhood friend of Wesley, a star on the school's football team, with whom she had fallen out during high school. She has a crush on guitar-playing Toby, and reluctantly attends a party hosted by mean-girl Madison, hoping to talk to him. The party turns out to be a disaster for her, as it is there that Wesley inadvertently reveals to her that she is the DUFF of her friend group—the Designated Ugly Fat Friend. He explains that the DUFF does not necessarily have to be ugly or fat, it is merely the person in a social group who is less popular and more accessible than the others in the group. People exploit the DUFF to get to the popular people.