What is fencing? Why were they not in England until the 16th century, and then they began?

In the 16th century, the industrial revolution was taking place throughout Europe. Trade has become much more intensive, the demand for raw materials has increased. Therefore, it became more profitable for English landowners to raise sheep and sell their wool to Flanders than to maintain the old subsistence economy. At the same time, many of the peasant tenants became “superfluous” people for the landowner.