CO2 is a colorless, odorless gas. It consists of one carbon atom and two oxygen atoms. Hence the name: carbon dioxide, which occurs naturally in the Earth's atmosphere. There, it plays a central role in the so-called carbon cycle. This is the process that regulates the exchange of carbon between the atmosphere, oceans, soil, plants and animals.

Plants, in turn, absorb CO2 from the air through photosynthesis and convert it into organic compounds. Oxygen is released. This process regulates the gas balance in the atmosphere and plant life. (Fabian Peters, more at basicthinking.de)