Carbon dioxide (CO2) 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 is essential for photosynthesis, the process by which plants convert sunlight into energy, using CO2 and water to produce oxygen and glucose. In addition to its natural sources, human activities have significantly increased CO2 levels, contributing to climate change. This greenhouse gas traps heat in the atmosphere, leading to global warming. Efforts to reduce CO2 emissions include using renewable energy sources and improving energy efficiency in industries and transportation.