The PPf frontier is the point at which an economy is most efficiently producing its goods and services. This means that at this frontier the resources are allocated at the best possible way.
All of the points inside a production possibilities frontier (PPF) are attainable. All of the points outside the production possibilities frontier are unattainable.
Attainable points can be reached while unattainable region is not capable of reaching at this point. However moving into the unattainable region would be better for the economy.
