Constructivism is a learning theory based on the idea that learning occurs as learners are actively involved in a process of meaning and knowledge construction as opposed to passively receiving information. Key aspects of constructivism include identifying student entry points, structuring experiences to help students build new understandings, using real-life projects to engage students, focusing on major concepts, and monitoring student understanding rather than assessing right and wrong answers. Major theorists who contributed to constructivism include Piaget, Bruner, Vygotsky, and Dewey. Constructivist classrooms encourage student collaboration, questioning, and interactive learning through scaffolding and social experiences.