The term "world's 20" most commonly refers to the G20, which is a group of 20 major economies. The G20 includes 19 countries plus the European Union, and since 2023, the African Union joined as the 21st member. These members are some of the world's largest and most influential economies, representing about 85% of global GDP, 75% of international trade, and about two-thirds of the global population. The G20 members are Argentina, Australia, Brazil, Canada, China, France, Germany, India, Indonesia, Italy, Japan, South Korea, Mexico, Russia, Saudi Arabia, South Africa, Turkey, the United Kingdom, the United States, the European Union, and the African Union.

If the query was about the world's 20 largest countries by area or population, here is a brief overview:

• By population, some of the top 20 countries are China, India, United States, Indonesia, Pakistan, Nigeria, Bangladesh, Russia, Mexico, and Japan.

• By area, the world's 20 largest countries include Russia, Canada, China, United States, Brazil, Australia, India, and Argentina among others.

For further focus, please specify if you mean the G20 economic group, the 20 largest countries by population, the 20 largest countries by area, or something else.