And why is our music called world music? I think people are being polite. What they want to say is that it's Third World music. Like they use to call us underdeveloped countries, now it has changed to developing countries, it's much more polite.
First, there was the three worlds model
The origin of the terminology is unclear. In 1952 Alfred Sauvy, a French demographer wrote an article in the French magazine L'Observateur which ended by comparing the Third World with the Third Estate. "Ce Tiers Monde ignoré, exploité, méprisé comme le Tiers État" (this ignored Third World, exploited, scorned like the Third Estate).  Other sources claim that Charles de Gaulle coined the term Third World, maybe de Gaulle only has quoted Sauvy.
The term First World refers to the developed, capitalist, industrial countries, generally aligned with NATO and the USA. The bloc of countries aligned with the United States after World War II, which had more or less common political and economic interests, this included the countries of North America and Western Europe, Japan, South Korea, and Australia.
Some African countries were assigned to the First World because of their links with Western countries. Western Sahara was part of Spain at that time. The anticommunist Apartheid Regime of South Africa was until May 1961, a member of the Commonwealth, and Namibia was then known as South West Africa and was administered by South Africa. Angola and Mozambique were run by the Portuguese like companies. (Historical footnote: Both countries became communist countries for some years in 1975.)
There were some "neutral" states in Europe, such as Switzerland, Sweden, Austria, Ireland, and Finland, but they can be classified as First World in this context.
Countries of the "First World"
The Second World refers to the former communist-socialist, less industrialized states known as the Eastern Bloc. The countries in the sphere of influence of the Soviet Union; it included the Soviet Socialist republics, the countries of Eastern and Central Europe, e.g., Poland, East Germany (GDR), Czechoslovakia, and the Balkans. And there were the Asian communist states in the sphere of influence of China, - Mongolia, North Korea, Vietnam, Laos, and Cambodia.
Countries of the "Second World"
The Third World was all the other countries. The mainly underdeveloped agricultural states and nations of Africa, Asia, and Latin America, where the blessings of civilization benefited only a small ruling elite and the corporations and upper classes of the former colonial powers.
In principle, the term Third World is outdated but still in use; today, the politically correct designation would be less developed countries.
What makes a nation Third World?
Nowadays, the term Third World is more often replaced by the terms Least Developed Countries (UN) or Low-Income Countries (World Bank.)
Whatever term is used, it serves to designate countries that suffer from high poverty, high child mortality, low economic and educational development, and low self-consumption of their natural resources. Countries that are vulnerable to exploitation by large corporations and industrialized nations.
These are the developing and technologically less advanced nations of Asia, Africa, Oceania, and Latin America. Third world nations tend to have economies dependent on the developed countries and are generally characterized as poor with unstable governments and having high fertility rates, high gender-related illiteracy and are prone to diseases. One of the critical factors is the lack of a middle class; there is a huge impoverished population and a small elite upper class that controls the country's wealth and resources. Most Third World nations also have very high foreign debt levels.
Countries of the "Third World"
Third World Countries classified by various indices: their Political Rights and Civil Liberties, the Gross National Income (GNI) and Poverty of countries, the Human Development of countries (HDI), and the Freedom of Information within a country.
The term "Fourth World" first came into use in 1974 with the publication of Shuswap Chief George Manuel's: The Fourth World: An Indian Reality (amazon link to the book). The term refers to nations (cultural entities, ethnic groups) of indigenous peoples living within or across state boundaries.
see Native American Indians
American Indian Nations.
More links to nations of the "Fourth World" you will find at the Nations Online Project respective country pages under "Natives."
The aftermath of the Second World War marked the beginning of a new era, characterized by the decline of all European colonial empires and the rise of two superpowers at the same time, the Soviet Union (USSR) and the United States (USA). In an attempt to avoid a third world war, the Allies created the United Nations.
The decline of the European colonial powers and the bipolar conflict of the superpowers had a decisive influence on the history of the Third World.
Growing political rivalry in the Arab world with conflicting ideologies was dubbed the Arab Cold War.
In one camp were the newly founded, more secular, pan-Arabic republics of North Africa and the Middle East, such as Syria, Iraq, Libya, North Yemen, and Sudan, led by Nasser's Egypt and inspired by the idea of Arab nationalism and socialism.
On the other side, led by King Faisal of Saudi Arabia, stood the newly founded oil-rich, sharia law wielding emirates on the Arabian Peninsula.
Despite ideological differences, the Arab world had an archenemy, Israel.
The founding of the State of Israel in 1948 led to a series of wars between 1948 and 1973 in which Arab states were involved in alternating alliances with Israel and its Western allies. The Arab–Israeli conflict is one of the major unresolved geopolitical conflicts in the world.
In 1931 a coup d'état forced Siam to change its status from an absolute monarchy to a constitutional monarchy; its name was changed in 1939 to Thailand.
Imperial Japan occupied Singapore from 1942 to 1945, after the fall of the British colony. The city was returned to British colonial rule in September 1945.
The US occupation of the Philippines ended after the Second World War and after almost 50 years of American rule in 1946.
The Dutch East Indies (today Indonesia), which comprised the southern islands in maritime Southeast Asia, had been in Dutch possession since the beginning of the 19th century.
The Japanese Empire occupied the Dutch colony during WWII, which ended the colonial rule of the Dutch. The Japanese occupation of Indonesia ended with Japan's surrender. Days after the Japanese submission, Sukarno, the leader of the country's struggle for independence, declared Indonesia's independence.
Japan occupied French Indochina during the Second World War, but the French were allowed to stay and exercise some influence. For administrative reasons, the Japanese created the new Empire of Vietnam, the Kingdom of Kampuchea (today Cambodia), and the Kingdom of Luang Phrabang (today Laos).
After WWII, the power vacuum in Vietnam was utilized by the Viet Minh, the only organized resistance group against French and Japanese occupation. The Viet Minh, led by Ho Chi Minh, launched the "August Revolution" in August 1945, seized control of Vietnam and declared Vietnamese independence, but it was a "fake independence." The French refused to let go of their colony. And far, far away in a German city at the Potsdam conference in July 1945, which was about to establish a general postwar order, the Allies divided Indochina into two zones at the 16th parallel. The rest is history. British forces, along with some French troops, arrived in Saigon, the capital of South Vietnam. Failing negotiations between the Vietnamese and the Allied Forces triggered a full-scale guerrilla war in December 1946 (First Indochina War).
The Division of Korea began at the end of World War II in 1945. In 1910, Imperial Japan annexed Joseon (Chosŏn), the dynasty that ruled the Korean peninsula. When Japan surrendered at the end of WWII, the peninsula was occupied by the Soviets and the US. They divided Korea into two zones along the 38th parallel; the Soviets settled in the north and the Americans in the south. The tensions between the two Koreas with their different ideologies led to the outbreak of the Korean War in 1950, which ended in a stalemate in 1953 without a formalized peace treaty.
To be continued