CO₂, or carbon dioxide, is a colorless, odorless gas that is naturally present in Earth's atmosphere. It is produced by the respiration of animals and plants, as well as through the combustion of fossil fuels like coal, oil, and natural gas. CO₂ plays a crucial role in the carbon cycle, helping to regulate the Earth's temperature by trapping heat in the atmosphere. In addition to its natural sources, CO₂ is also used in various industrial applications, such as in the production of carbonated beverages and as a refrigerant. Elevated levels of CO₂ in the atmosphere are linked to climate change, making it an important focus for environmental science and policy, particularly in discussions about global warming and sustainable energy.