Constructivism is a learning theory where students actively construct their own understanding and knowledge through experiences and reflecting on those experiences. Key theorists who influenced constructivism include Piaget, Bruner, Vygotsky, and Dewey. They believed that students learn best through doing, exploring, and socially interacting with peers and teachers, rather than through lecture-based learning. Constructivism focuses on the active role of the learner in building knowledge and emphasizes critical thinking over memorization.