The same logic applies to countries. Each country should specialize in producing those things that it produces most efficiently, rather than producing a bit of everything, because that way its income will be higher.
同样的逻辑也适用于国家。各国都应该专注于生产它们生产效率最高的产品，而不是所有东西都生产一些，因为这样能让该国的收入有所提高。