The creation of fossil fuels and the movement of carbon into the ground
The Carbon Cycle is a great and vast process of carbon being cycled through the ground, air, plants, animals & fossil fuels. The "first" part is when carbon moves from the atmosphere to plants through the process of photosynthesis.
Carbon moves from plants to animals. Through the food chain, the carbon that is in plants transfers to animals that eat them. And animals that eat other animals get the carbon from the food they eat.
Burning Fossil Fuels
Next Carbon moves from plants and animals to the soil. When plants and animals perish, their remains bring carbon into the ground. Some will be buried and become fossil fuels in due time.
Under the sea
Also carbon is moved from living things to atmosphere. Due to the process of cellular respiration, animals exhale carbon dioxide (CO2) into the air.
Additionally carbon is released from fossil fuels into the atmosphere. This happens when humans burn fossil fuels to power cars, factories, power plants, and other things too.
LAstly carbon is moved from the atmosphere into the oceans. The oceans, and similar bodies of water, absorb some carbon from the air. Then it is dissolved in the water.