Erik Erikson's Stages of Development is a theory that outlines eight key phases individuals go through from infancy to adulthood. Each stage presents a unique psychological challenge or conflict that must be resolved for healthy emotional and social development. Successful resolution leads to a stronger sense of self and well-being, while failure can result in difficulties in later stages. The stages include Trust vs. Mistrust in infancy, Autonomy vs. Shame and Doubt in early childhood, and Identity vs. Role Confusion during adolescence, among others. Each stage builds on the previous ones, emphasizing the importance of social relationships and personal growth throughout life.