PHOTOSYNTHESIS

Photosynthesis 
is a process used by plants and other organisms to capture the sun's energy to split off water's hydrogen from oxygen. Hydrogen is combined with carbon dioxide (absorbed from air or water) to form glucose and release oxygen. All living cells in turn use fuels derived from glucose and oxidize the hydrogen and carbon to release the sun's energy and reform water and carbon dioxide in the process of cellular respiration

Light reaction VS Dark Reaction

Light Reaction (involves the sun)

The roots suck up water from the ground, into the chloroplasts. 

In there, the water is sun-heated and gets split into hydrogen, oxygen and ATP. 

The oxygen then gets released for us to breath and the hydrogen is put to a different part of the leaf.

Dark Reaction (doesn't involve the sun)
After the hydrogen gets to the other part of the leaf, the CO2 (carbon dioxide), 

that we breath out, 

mixes with the hydrogen and gets fused using ATP, making sugar/starch.

Calvin cycle, Calvin–Benson-Bassham (CBB) cycle, reductive pentose phosphate cycle or C3 cycle is a series of biochemical redox reactions that take place in the stroma of chloroplasts in photosynthetic organisms. It is also known as the dark reactions.

Photosynthesis occurs in two stages. In the first stage, light-dependent reactions capture the energy of light and use it to make the energy-storage molecules ATP and NADPH. The light-independent Calvin cycle uses the energy from short-lived electronically excited carriers to convert carbon dioxide and water into organic compounds that can be used by the organism (and by animals that feed on it). This set of reactions is also called carbon fixation. The key enzyme of the cycle is called RuBisCO. In the following biochemical equations, the chemical species (phosphates and carboxylic acids) exist in equilibria among their various ionized states as governed by the pH.

The enzymes in the Calvin cycle are functionally equivalent to many enzymes used in other metabolic pathways such as gluconeogenesis and the pentose phosphate pathway, but they are to be found in the chloroplast stroma instead of the cell cytoplasm, separating the reactions. They are activated in the light (which is why the name "dark reaction" is misleading), and also by products of the light-dependent reaction. These regulatory functions prevent the Calvin cycle from being respired to carbon dioxide. Energy (in the form of ATP) would be wasted in carrying out these reactions that have no net productivity.

calvin cycle equation.

3 CO₂ + 6 NADPH + 5 H₂O + 9 ATP → glyceraldehyde-3-phosphate (G3P) + 2 H⁺ + 6 NADP⁺ + 9 ADP + 8 P_i