This document provides an overview of literary theory and the major theories that have influenced the study of literature. It discusses theorists like Marx, Freud, Nietzsche and Darwin who shaped modern thought. Some key theories mentioned include formalism, structuralism, reader-response theory, poststructuralism, feminism and queer theory. The document also addresses what literary theory is used for, such as providing better understanding, interpretation and appreciation of texts, culture and different perspectives.