Constructivism is a learning theory that posits that people actively construct their own understanding and knowledge of the world through experiencing things and reflecting on those experiences. It sees learning as an active, contextualized process of constructing knowledge rather than acquiring it. Key contributors to constructivism include Piaget who saw children as active learners constructing knowledge through stages, Vygotsky who emphasized social learning and culture, and Dewey who felt learning should be engaging. In constructivist classrooms, teachers organize information and prompt student questions, while students build on prior knowledge through inferences and relationships between ideas.