US and NATO countries were the first world, communism/Soviet Union was the second world, and the non-aligned countries were the third world. The first and second worlds would fight over the third worlds.
You are, of course, referring to the few countries that have torn themselves loose from the old USSR. The whole of South America, Africa, and Asia with their assorted countries were the 3rd world. The UN has 193 member states - of them, about 173 were considered 3rd world. The actual count depends on when during the cold war you want to count the countries and how you count them (are n/s Korea and N/S VIET NAM 2 OR 4 countries).
Go to your local used book store and pick up a copy of Howard Zinn's A People's History of the United States - don't try to read it in one sitting, just keep it around and when something comes up, take a look at a 'different' point of view.
What happens to a dream deferred?
Does it dry up
like a raisin in the sun?
Or fester like a sore-
And then run? Does it stink like rotten meat? Or crust and sugar over- like a syrupy sweet?