Final answer:
Core nations possess highly industrialized economies with advanced service sectors and high income levels, distinguishing them from semi-peripheral and peripheral nations.
Step-by-step explanation:
The world's core nations are those with highly industrialized economies, advanced technological infrastructure in industrial, administrative, and service sectors, and a high level of national and personal income. Nations such as the United States, Canada, members of the European Union, Japan, and more recently, emerging economies like China and Mexico, fall into this category.
These countries have moved beyond heavy reliance on the primary sector of economic production, like agriculture, toward dominance in the tertiary or service sector. In contrast to core nations, semi-peripheral nations fill an intermediary position, acting as both providers of raw materials and markets for core nation's goods while exploiting cheaper labor from peripheral nations. Peripheral nations are on the fringes, with limited industrialization and a workforce primarily employed in primary sector activities. As countries develop economically, they tend to move from a focus on the primary sector to the secondary sector, and eventually, as in the case of core nations, to a predominantly service-based economy.