What is the purpose, audience and tone for a short story?I have to fill out a prewriting sheet, but I don't know what these are.

Each of these three literary devices will be different depending upon the short story in question.

AUDIENCE. The audience is the actual person or persons who will be reading the story. A writer may aim his story at a specific age group (adolescents or the retired, for example) or for a more limited group (such as an English class or an Internet blog), but he should always anticipate their needs or expectations.

PURPOSE. The writer's purpose may be to inform, convince, learn something new, shock, draw a conclusion or create sympathy, to name a few. It may be simply to mystify and then surprise with an unexpected ending, which is a major element of all good short stories.

TONE. The author's tone is an emphasis of the attitude that he wishes to express for each story. An author's tone can be "characterized as serious or ironic, sad or happyy, private or public, angry or affectionate, bitter or nostalgic, or any other attitudes and feelings that human beings experience." (The Bedford Introduction to Literature, Sixth Edition, p. 2213.)