A carbon offset is a unit of measurement representing the reduction, avoidance, or removal of one metric ton of carbon dioxide (CO2) or its equivalent greenhouse gas emissions from the atmosphere. It is a mechanism used to compensate for or offset the emissions generated by an individual, organization, or activity by supporting projects that reduce emissions or remove carbon dioxide from the atmosphere.

The concept of carbon offsets is based on the principle that greenhouse gas emissions have a global impact on climate change, regardless of where they occur. By investing in projects that reduce emissions elsewhere, carbon offsets help to achieve a net reduction in global emissions and contribute to climate change mitigation.

Carbon offset projects can take various forms, including:

1. Renewable Energy: Projects that generate clean energy from renewable sources like wind, solar, hydro, or biomass, displacing the need for fossil fuel-based energy generation.
2. Energy Efficiency: Initiatives that promote energy efficiency and conservation measures, reducing energy consumption and associated emissions.
3. Forestry and Reforestation: Projects that involve afforestation (planting new forests) or reforestation (restoring deforested areas), as trees absorb and store carbon dioxide through photosynthesis.
4. Methane Capture: Projects focused on capturing and utilizing or destroying methane emissions from sources like landfills, agricultural activities, or wastewater treatment plants.
5. Agricultural Practices: Initiatives that implement sustainable agricultural practices, such as reducing methane emissions from livestock or implementing carbon sequestration techniques in farming.
6. Industrial Processes: Projects aiming to reduce emissions from industrial activities or capture and store carbon emissions, such as carbon capture and storage (CCS) technologies.

When an individual or organization purchases carbon offsets, they are effectively investing in these projects to compensate for their own emissions. The carbon offset units they purchase represent the equivalent emissions reductions achieved by the supported projects.

It is important to note that while carbon offsets can play a role in mitigating climate change, they should not be seen as a substitute for efforts to reduce emissions at their source. The primary focus should be on implementing measures to minimize emissions and transition to a low-carbon economy. Carbon offsets should be used as a complementary tool to achieve further emissions reductions beyond what can be achieved internally.