Why such different countries of Asia and Africa can be united by the concept of the third world?

Why such different countries of Asia and Africa can be united by the concept of the third world? Why is the Korean War considered one of the high points of the Cold War?

The concept of the third world, invented by interested parties, in order to emphasize, is not the ability of these states to self-government. And on the basis of this, for their own benefit, constantly interfere in the internal affairs of these countries. The Korean War is considered one of the high points of the Cold War, because between mortal enemies, it cannot be otherwise. Aggravation of relations between two hostile camps can only have such epithets: the highest point, extreme tension, on the verge, and so on.