The carbon dioxide is a chemical compound composed of a carbon atom and two oxygen atoms and whose raw formula is: CO2.
This line molecule has a Lewis developed formula: O=C=O
Under the normal conditions of temperature and pressure the carbon dioxide is a colourless gas commonly called carbon gas.
It is present in the atmosphere in a proportion roughly equal to 0,035 % in volume.
It is a gas of greenhouse effect
It is produced notably at the time of aerobic fermentation or combustion of organic compounds, and at the time of the breathing of the living beings and the plants. For those lasts, the photosynthesis entraps much more CO2 than their breathing does not produce any.