Constructivism is a theory of learning that suggests humans construct knowledge and meaning from their experiences. Key theorists like Piaget and Dewey influenced the development of constructivism and progressive education. Constructivism posits that learning is an active process where learners build on prior knowledge through experiences. For teachers, this implies facilitating learning through meaningful lessons and encouraging collaboration. The 5Es model - engage, explore, explain, elaborate, evaluate - provides a framework for lesson planning based on constructivist principles.