Production Possibility Curve

the point A shows that the productivity is not achievable with the current technology and resources, and the point B shows that the point is can achievable but not very efficiently allocated because the resources are not fully used, the line from X axis to Y axis show the resources are fully allocated. 

The PPC may shift from time to time, gaining or losing resources, increase in quality of technology can increase the resources to fully efficiently used, if both good X and Z increase there could be an economic growth happening in the country .