Photosynthesis is a process of the plant absorbing the sun raze and the water and transforming it into chemical so they can live a produce oxygen for us to live.
During the day the tree absorbs CO2 and makes it into energy and sugars. During the night they use the sugars and energy to keep the plant living because there is no sunliught.
The light dependent reaction use the carbon and turns into ATP and then the ATP go back into the clavin cycle and then the clavin cycle turns it into NDAP+ then after all that the plant stores it and uses it for later when the sun isn't out.