is a term with a range of meanings. It is used, inter alia, to describe perspectives on learning that see the learner as actively constructing knowledge by interpreting experience (rather than, say, considering that knowledge can be transferred directly from one person to another)
Read about 'Constructivism'
Read: Constructivism in Education: Interpretations and Criticisms from Science Education (Book chapter)
Read: Constructivism as educational theory: Contingency in learning, and optimally guided instruction (Book chapter)