Every year, the U.N. climate conference conjures hundreds of headlines on global efforts to spare the world from climate catastrophe. This year’s begins on Monday in the Brazilian rainforest city of Belem.

But what exactly happens at these annual summits? Here’s what you need to know:

The treaty, called the U.N. Framework on Climate Change Convention (UNFCCC), committed countries to working together to fight climate change – a problem they acknowledged all countries faced and was best tackled together.

The treaty also established the principle of “common but differentiated responsibilities”, meaning the rich countries responsible for most of the planet-warming emissions bear a greater responsibility in solving the problem.

The rotating presidency, now held by Brazil, sets the summit agenda and works through the year to rally governments toward shared action and goals. It then hosts the two-week summit, drawing global attention to the issue while giving national leaders a chance to swap ideas and hold one another accountable.

Over the years, the annual summits have become a major hub of geopolitical and financial discussion – projecting the idea of a “global village” that welcomes all countries, civil society groups, businesses and financiers.

WHY SHOULD WE CARE ABOUT COP30 THIS YEAR?

For many, this year’s 30th climate summit marks as a full-circle moment.

Brazil had hosted the Rio Earth Summit where the UNFCCC treaty was signed 33 years ago. This year, the country insisted the event would return to its roots in acknowledging the world’s most vulnerable including indigenous groups, with some joining the talks.

Brazil has asked countries to work on realizing past promises, such as a COP28 pledges to phase out fossil fuel use, rather than making new ones. COP30 is also the first to acknowledge failure in meeting the past goal of preventing warming above 1.5 degrees Celsius.

Brazil opted to hold COP30 in the Amazon city of Belem – hoping to symbolically underline the importance of world forests that remain targets for logging and industries including mining, farming and fossil fuel extraction.

WHO ARE THE MAIN PLAYERS AT THE SUMMIT?

Most national governments send teams to the talks. Often, countries speak together in groups with similar interests.

Some of the more prominent voices include the Alliance of Small Island States facing an existential threat from rising seas, and the G77+China bloc of developing countries.

Also influential are the Africa Group and the BASIC Group consisting of Brazil, South Africa, India and China.

The US, which pledged in January to quit the Paris Treaty on climate change, has stepped away from its past leadership role. China, Brazil and others have stepped in to fill the void.

TWO WEEKS SEEMS A LONG TIME – WHAT HAPPENS AT THE SUMMIT?

The sprawling COP campus is often a hive of activity, with campaigners trying to draw attention to their causes while corporations lobby policy change and seek business deals.

This year has been unique in sloughing off the usual side events and leaving financiers to meet in Sao Paulo while local leaders huddled in Rio de Janeiro. Those events, along with a meeting of world leaders in Belem, were staged before the November 10-21 COP30 in hopes of generating support and momentum for climate action for the actual talks.

During the summit’s first week, country negotiators will lay out their priorities and gauge one another’s positions. Themes should begin to emerge, while countries and companies announce action plans and pledges of financing for projects.

Negotiators are typically joined by national ministers during the second week, to haggle over final decisions including legal and technical details.

THAT SEEMS EASY, RIGHT?

COPs rarely run smoothly, with countries jockeying for deals in their national interest and drawing red lines. The talks can sometimes stall out and lead to acrimony.

Toward the end, negotiators often spend frantic all-night sessions seeking compromises. Countries then reconvene to approve decisions – by consensus, not unanimity.

The closing session, when the hammer of a gavel marks the end of the summit, is almost always delayed - sometimes by several days. Bring snacks.