Kohlberg's stages of moral development describe 6 stages grouped into 3 levels - preconventional, conventional, and postconventional. At the preconventional level, morality is based on obedience and self-interest. The conventional level focuses on maintaining relationships and social order. The postconventional level assesses morality based on individual rights and universal ethical principles. Kohlberg believed people progress sequentially through these stages as their reasoning becomes more sophisticated.