Kohlberg's theory of moral development proposes that morality develops through three levels - preconventional, conventional, and post-conventional. At the preconventional level, children's judgments are based on external consequences like punishment. At the conventional level, judgments are based on social norms and expectations. At the post-conventional level, individuals recognize morality as separate from social conventions and base right and wrong on respect for others and internal ideals. Kohlberg proposed six stages across these three levels to describe how morality develops from a concern with obedience and self-interest to social order and finally to abstract ethical principles.