Zone of proximal development
1) When instruction is laid out on a scale of difficulty from easy to hard, there is a region where the instruction is too hard for the student to learn effectively from it without help, but still just easy enough that the student can learn if given help, typically from a second agent. This region is called the zone of proximal development (ZPD), a term from developmental psychology.
2) Vygotsky (1978) maintained the child follows the adult's example and gradually develops the ability to do certain tasks without help or assistance. He called the difference between what a child can do with help and what he or she can do without guidance the "zone of proximal development" (ZPD). (sourc-North Central Regional Educational Laboratory)
3) The gap between a learner's current or actual development level determined by independent problem-solving and the learner's emerging or potential level of development.