Whey are they called 3rd world countries?

Answer 1

The term Third World arose during the Cold War to define countries that remained non-aligned or neutral with either capitalism and NATO (which along with its allies represented the First World) or communism and the Soviet Union (which along with its allies represented the Second World). This definition provided a way of broadly categorizing the nations of the Earth into three groups based on social, political, and economic divisions. Although the term continues to be used colloquially to describe the poorest countries in the world, this usage is widely disparaged since the term no longer holds any verifiable meaning after the fall of the Soviet Union deprecated the terms First World and Second World. While there is no identical contemporary replacement, common alternatives include developing world and Global South.