Genre fiction, also known as popular fiction, is plot-driven fictional works written with the intent of fitting into a specific literary genre, in order to appeal to readers and fans already familiar with that genre. Genre fiction is generally distinguished from literary fiction. Screenwriting teacher Robert McKee defines genre conventions as the "specific settings, roles, events, and values that define individual genres and their subgenres". These conventions, always fluid, are usually implicit, but sometimes are made into explicit requirements by publishers of fiction as a guide to authors seeking publication. There is no consensus as to exactly what the conventions of any genre are, or even what the genres themselves are; assigning of works to genres is to some extent arbitrary and subjective.