 In schools, this feedback is almost entirely thought of as the teacher providing feedback to the student.The idea of providing feedback to advance student learning is best understood in the framework of the "zone of proximal development" or ZPD.Psychologist Lev Vygotski has defined the ZPD as "the distance between the actual developmental level as determined by independent problem solving and the level of potential development as determined through problem solving under adult guidance or in collaboration with more capable peers".