The golden billion is a term to describe the world's most affluent and developed countries. It refers to the approximately one billion people who live in the Western industrialized nations of North America and Western Europe (sometimes Japan included); it was not widely used in the English-speaking world but widespread in the former Soviet Union.
The term was used by Soviet economists to describe the wealthy countries of the West, who they believed had achieved an unprecedented level of prosperity and standard of living.
Usually the terms "first world", "developed world" or "high-income countries" is used to describe this concept.
Wikipedia writes: "The golden billion theory is a conspiracy theory that a cabal of global elites are pulling strings to amass wealth for the world's richest billion people at the expense of the rest of humanity."