During the the learning process, a child begins by basically copying an adult's example; the child is initially unable to achieve a given task without assistance. However the child is, at that time, capable of achieving more complex tasks with adult assistance. The difference between these two accomplishments is called the Zone of Proximal Development.
A child's ZPD is constantly changing as he or she masters increasingly challenging tasks with time.
In Education, consideration of the concept of ZPD is useful because it reminds teachers of how children can be stretched to reach higher level learning goals with adult guidance and support.
ZPD was established by the Russian psychologist Lev Vygotsky.