This document provides an overview of several major career development theories. It begins by defining what a theory is and what purpose theories serve. The document then outlines the "Big Seven" career development theories: 1) Trait and Factor Approaches, 2) Holland's Theory of Personality Types, 3) Development Theories including Super's Theory of Vocational Development and Gottfredson's Theory of Circumscription and Compromise, 4) Learning and Cognitive Theories, 5) Theories of Embedded Career, 6) Psychodynamic Approaches, and 7) Anne Roe's Work Adjustment Theory. For each theory, the document briefly describes the origin and key concepts or principles of the theory.