From the announcement:
Where are we? Who is there? What's going on? And how is it all going to end? These are the crucial questions each player answers, choosing from the cards they're dealt to tell a very short story. Players combine Settings, Characters, Problems, and Resolutions to create a story they then tell to the other players.
Nanofictionary is a story-telling game in three rounds. In the first phase, everyone builds a collection of story elements, featuring at least one of each type.
Next, players take turns telling a brief story based on the ideas in the set of cards they selected.
Lastly, everyone votes for the story they liked best (besides their own). Whoever gets the most votes wins!