What does it mean for an economy to be operating on its PPF?

When an economy is operating on its Production Possibility Frontier (PPF), it means that the economy is utilizing all of its resources efficiently. The PPF represents the maximum possible output combinations of two goods or services that can be produced with available resources and technology, showing the trade-offs between them.

Being on the frontier indicates that resources are fully employed and there is no waste; the economy is producing at its highest potential given the current inputs. Thus, all available labor, capital, and land are being used in such a way that reallocating resources would lead to a decrease in the output of one good without increasing the output of another. This concept is fundamental in understanding efficiency in production and the opportunity cost associated with choosing one good over another.