Lev Vygotsky was a Russian psychologist known for his work in developmental psychology and education. He introduced the concept of the Zone of Proximal Development (ZPD), which describes the difference between what a learner can do independently and what they can achieve with guidance. Vygotsky emphasized the importance of social interaction in learning, suggesting that collaboration with more knowledgeable others enhances cognitive development. His theories highlight the role of culture and language in shaping thought processes. Vygotsky believed that learning is a social process, where communication and cultural tools play a crucial role in helping individuals acquire new skills and knowledge.