Development theories are frameworks that explain how individuals grow and change throughout their lives. These theories often focus on various aspects of development, such as cognitive, emotional, and social growth. Notable theorists include Jean Piaget, who studied cognitive development in children, and Erik Erikson, who proposed stages of psychosocial development. These theories help educators, psychologists, and parents understand the processes behind learning and behavior. By applying these concepts, they can create supportive environments that foster healthy development. Additionally, development theories can inform policies and practices in fields like education and mental health.