The document discusses Lev Vygotsky's socio-cultural theory of development. It explains that Vygotsky believed cognitive development occurs through social interactions and is mediated by language and culture. A key concept is the Zone of Proximal Development, which is the difference between what a child can do independently and what they can do with guidance and is the area where maximum learning occurs. Scaffolding from adults and peers helps children learn new skills within their ZPD."