Queer theory challenges traditional notions of gender and sexuality, emphasizing fluidity and non-binary perspectives. It emerged in the late 1980s, drawing from feminist theory and LGBT studies, and has since expanded to encompass a wide range of identities and experiences. Key concepts include heteronormativity, gender performativity, and intersectionality. Major theorists like Judith Butler and Eve Kosofsky Sedgwick have significantly shaped the field, exploring how gender and sexuality are constructed and performed in society.