Critical Theory is a school of thought practised by the Frankfurt School theoreticians (i.e., Herbert Marcuse, Theodor Adorno, Walter Benjamin, Erich Fromm, and Max Horkheimer). Horkheimer described a theory as critical insofar as it seeks to liberate human beings from the circumstances that enslave them.
A critical theory is any approach to social philosophy that focuses on society and culture to reveal, critique and challenge power structures. It argues that social problems stem more from social structures and cultural assumptions than from individuals. It views ideology as the principal obstacle to human liberation.