In the pantheon of global gatherings, the G20 is the main forum for economic and financial cooperation — areas increasingly tested by today’s shifting geopolitics.

The Group of Twenty brings together the world’s biggest economies. It is made up of 19 nations, including the United States and China, and two regional organizations: the European Union and African Union.

Here is a primer on the G20 and what it does:

Who is in the G20?

Despite its name, the G20 today counts 21 members.

The 19 countries in it are: Argentina, Australia, Brazil, Britain, Canada, China, France, Germany, India, Indonesia, Italy, Japan, Mexico, Russia, Saudi Arabia, South Africa, South Korea, Turkey, and the United States.

Together, they account for 85 percent of global GDP and three-quarters of global trade.

The European Union has also long been a member, with the African Union admitted last year.

How did it come about?

The G20 was conceived in 1999, in response to the Asian financial crisis two years prior that shook the global system. It was originally designed as a coordination space for finance ministers and central bank chiefs.

It was elevated to leader-level in 2008 — after another global financial crisis — so heads of state and government could meet annually on international economic issues.

The gathering also encompasses side forums where representatives discuss topics such as health, culture, social justice, agriculture, tourism and fighting corruption.

What’s happening this G20?

Brazil holds the rotating G20 presidency this year and has made fighting hunger, poverty and inequality its priorities, along with sustainable development and reforming global governance.

To back that up, it is holding a G20 Social forum days before the main November 18-19 event, designed to boost civil society’s voice in the governments’ discussions.

The G20 summit is taking place in Rio de Janeiro and will see US President Joe Biden attend alongside China’s Xi Jinping and other leaders.

Russian President Vladimir Putin announced last month he would not be traveling to Brazil.

He said his presence would “wreck” the summit, but insisted an International Criminal Court arrest warrant out against him for Russia’s actions in Ukraine was not a factor in his decision. Foreign Minister Sergei Lavrov is going in his place.

Past frictions

Recent G20s demonstrated discord between participating countries over Russia’s war in Ukraine.

The last two summits, in Bali in 2022 and Delhi in 2023, had to ditch the traditional “family photo” of the leaders standing together in a symbol of unity because of different stances toward Moscow and how to characterize the war.

Xi also upbraided Canadian Prime Minister Justin Trudeau at the Bali summit after details of talks they held were leaked to the media.