Constructivism is a learning theory that suggests students actively construct their own understanding and knowledge through experiences and reflecting on those experiences. Key aspects include students learning by doing rather than passively receiving information, and the idea that knowledge is constructed by learners based on their experiences. Major advocates include Piaget, Bruner, Vygotsky, and Dewey. In a constructivist classroom, students would interact with knowledge through experimentation, inquiry, and technology to actively build their own understanding.