The trading of carbon credits is done between countries in the so-called carbon market, and characterises the sale of credits between a country that holds them, having reduced its carbon dioxide emissions, and a country that needs to reduce its emissions, but did not achieve its goals. This market exists all over the world, and is regulated in each country by legislation, which defines the particularities of trading. In Brazil, the market is regulated through Decree 5,882 of 2006. Commercialisation is carried out in accordance with the rules of the Clean Development Mechanism (CDM), which can be unilateral, bilateral or multilateral, and allows cooperation between industrialised countries and developing countries.

The carbon credits market is a mechanism that allows organizations to offset their greenhouse gas (GHG) emissions by purchasing carbon credits generated by projects that promote the reduction or removal of these emissions. There are two types of carbon credit markets: the regulated market and the voluntary market.

The regulated carbon credits market is established by governments or regulatory bodies, which create GHG emissions reduction targets for companies and industries in their territories. Companies that fail to meet their emissions reduction targets are forced to purchase carbon credits to offset their excess emissions. This market is regulated and priced by rules and standards established by governments or regulatory bodies and is generally restricted to certain sectors or geographic regions.

The voluntary carbon credit market is established by companies, non-governmental organizations (NGOs) and individuals who wish to offset their GHG emissions voluntarily. In this market, companies and individuals buy carbon credits generated by projects that promote the reduction or removal of GHG emissions, without the regulatory obligation to do so. This market is not regulated by government rules, but is generally governed by certification standards established by non-governmental organizations, such as the Verified Carbon Standard (VCS) or the Gold Standard. Although licenses are negotiated bilaterally or on markets and exchanges, there are differences between credits: whether they reduce, avoid or remove emissions; from which activities or region they originate; what co-benefits they create; between others. However, regulated and voluntary markets can connect, as some regulated markets allow a small portion of targets to be met through voluntary carbon credits.

The carbon market began with the creation of the United Nations Framework Convention on Climate Change (UNFCCC) during the COP 92 in Rio de Janeiro, with the aim of stabilising the concentration of greenhouse gases (GHG) in the atmosphere . It emerged as a tool to face the challenge of climate change and reduce greenhouse gas (GHG) emissions at a global level. The Kyoto Protocol, an international agreement on climate change adopted in 1997, was an important milestone in the development of the carbon market.

Since then, the carbon market has grown and evolved, with various types of carbon credits being created, such as renewable energy and reforestation credits, and new carbon markets emerging around the world. Today, the carbon market is an important tool for tackling climate change, helping companies and governments to reduce their GHG emissions more economically and efficiently.