Constructivism is a learning theory that states students learn by actively constructing knowledge based on experiences. Key aspects are that learning is student-centered rather than curriculum-centered, and that students learn by doing and forming their own understandings. Major contributors include Piaget, who developed theories of cognitive development, Bruner, who emphasized active learning, and Vygotsky, who explored social influences on learning. In the classroom, teachers act as guides rather than instructors, create learning experiences that build on student knowledge, and encourage collaboration, allowing students to take responsibility for and direct their own learning.