A movement along a production possibilities curve (PPC) shows the trade-offs society faces when reallocating resources between the production of two goods. Specifically, it reflects how increasing the production of one good results in the decrease of the other due to limited resources, illustrating opportunity cost. This movement assumes the total resources and technology remain unchanged, and the economy is operating efficiently on the curve. Thus, a movement along the PPC represents a change in the allocation of existing resources between the two goods, demonstrating the concept of opportunity cost and productive efficiency