This document provides an overview of Lev Vygotsky's sociocultural theory, including its four basic principles: 1) language plays a central role in development, 2) development cannot be separated from its social context, 3) learning can lead development, and 4) children construct their own knowledge. It discusses key concepts such as the zone of proximal development and internalization. The history of sociocultural theory is also briefly outlined, noting contributions from Vygotsky, Luria, Leontiev, and Lantolf.