The term "Third World" arose during the Cold War to define countries that remained non-aligned with either NATO or the Warsaw Pact. The United States, Canada, Japan, South Korea, Western European nations and their allies represented the "First World", while the Soviet Union, China, Cuba, Vietnam 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. Since the fall of the Soviet Union and the end of the Cold War, the term Third World has decreased in use. It is being replaced with terms such as developing countries, least developed countries or the Global South. The concept itself has become outdated as it no longer represents the current political or economic state of the world and historically poor countries have transited different income stages.
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. In the dependency theory of thinkers like Raúl Prebisch, Walter Rodney, Theotônio dos Santos, and Andre Gunder Frank, the Third World has also been connected to the world-systemic economic division as "periphery" countries dominated by the countries comprising the economic "core".
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 economically poor and non-industrialized, it became a stereotype to refer to developing countries as "third world countries", yet the "Third World" term is also often taken to include newly industrialized countries like Brazil, China and India 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 Austria, Finland, Ireland, Sweden and Switzerland.