What is the exposition?

In Chapter One, the story's exposition begins with Harriet, who lives on the Upper East Side of Manhattan, teaching her friend Sport how to play Town. Harriet makes up all the names, families, and occupations of people living in her town, and then she writes them all down in her notebook, and although Harriet is determined to get Sport to use his imagination to help with their town..... he isn't overly interested.