The term “Third World” arose during the Cold War to define countries that remained non-aligned with either NATO or the Communist Bloc. The United States, Canada, Japan, South Korea, Western European nations and their allies represented the First World, while the Soviet Union, China, Cuba, and their allies represented the Second World. This terminology provided a way of broadly categorizing the nations of the Earth into three groups based on political and economic divisions.
The Third World was normally seen to include many countries with colonial pasts in Africa, Latin America, Oceania and Asia. It was also sometimes taken as synonymous with countries in the Non-Aligned Movement.
Due to the complex history of evolving meanings and contexts, there is no clear or agreed-upon definition of the Third World. Some countries in the Communist Bloc, such as Cuba, were often regarded as “Third World”. Because many Third World countries were extremely poor, and non-industrialized, it became a stereotype to refer to poor countries as “third world countries”, yet the “Third World” term is also often taken to include newly industrialized countries like Brazil, India and China now more commonly referred to as part of BRIC. Historically, some European countries were non-aligned and a few of these were and are very prosperous, including Ireland, Austria, Sweden, Finland, and Switzerland.
The Fourth World is an extension of the Three-World Model, used variably to refer to
Sub-populations socially excluded from global society;
Hunter-gatherer, nomadic, pastoral, and some subsistence farming peoples living beyond the modern industrial norm.
Sub-populations existing in a First World country, but with the living standards of those of a Third World, or developing country.
The term is not commonly accepted and “Fourth World” has also been used to refer to other parts of the world in relation to the Three-World Model.