To close the gap of information you will find here explanations of the terms.
The use of the terms First, the Second, and the Third World is a rough, and it's safe to say, outdated model of the geopolitical world from the time of the cold war.
There is no official definition of the first, second, and the third world. Below OWNO's explanation of the terms.
Four Worlds
After World War II the world split into two large geopolitical blocs and spheres of influence with contrary views on government and the politically correct society:
1 - The bloc of democratic-industrial countries within the American influence sphere, the "First World".
2 - The Eastern bloc of the communist-socialist states, the "Second World".
3 - The remaining three-quarters of the world's population, states not aligned with either bloc were regarded as the "Third World."
4 - The term "Fourth World", coined in the early 1970s by Shuswap Chief George Manuel, refers to widely unknown nations (cultural entities) of indigenous peoples, "First Nations" living within or across national state boundaries.
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. However...
__ Definitions
The term "First World" refers to so called developed, capitalist, industrial countries, roughly, a bloc of countries aligned with the United States after World War II, with more or less common political and economic interests: North America, Western Europe, Japan and Australia. 
Countries of the "First World" "Second World" refers to the former communist-socialist, industrial states, (formerly the Eastern bloc, the territory and sphere of influence of the Union of Soviet Socialists Republic) today: Russia, Eastern Europe (e.g., Poland) and some of the Turk States (e.g., Kazakhstan) as well as China. Countries of the "Second World" "Third World" are all the other countries, today often used to roughly describe the developing countries of Africa, Asia and Latin America.The term Third World includes as well capitalist (e.g., Venezuela) and communist (e.g., North Korea) countries, as very rich (e.g., Saudi Arabia) and very poor (e.g., Mali) countries.
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.
What makes a nation third world?
Despite everevolving definitions, the concept of the third world serves to identify countries that suffer from high infant mortality, low economic development, high levels of poverty, low utilization of natural resources, and heavy dependence on 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 rates of population growth, illiteracy, and disease. A key factor is the lack of a middle class — with impoverished millions in a vast lower economic class and a very small elite upper class controlling the country's wealth and resources. Most third world nations also have a very large foreign debt.
(What makes a nation third world? from Encyclopedia of World Geography)
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 (nation states).Read more
