Third World Countries

They are not primitive, underdeveloped, or poor, as many believe. A third world country is just a country that is not considered a capitalist country (first world) or a communist country (2nd world). The terms “first world” and “second world” virtually disappeared from usage after the fall of the Soviet Union.
 
The terminology came about just after WWII with the “first world” countries that were aligned with the United States common political and economic structure (capitalists). Second world countries were those that aligned with the Soviet Union in terms of their political and economic structure (communists and socialists). Third world countries were the rest that were not aligned with either, whether poor or not.

Correct term to refer to poor or underdeveloped countries is “Developing World”.