Photosynthesis is a process used by plants, algae, and certain bacteria to convert light energy, usually from the sun, into chemical energy.

There are two major parts of photosynthesis: the light-dependent reactions and the light-independent reactions (also known as the Calvin Cycle).

1. Light-dependent reactions: These reactions occur in the thylakoid membranes of the chloroplasts where light energy is converted into chemical energy (ATP and NADPH). The light-dependent reactions generate oxygen as a byproduct due to the splitting of water molecules (photolysis).

2. Light-independent reactions (Calvin Cycle): These reactions occur in the stroma of the chloroplasts. The ATP and NADPH produced in the light-dependent reactions drive the conversion of carbon dioxide to glucose (carbohydrate), through a cycle of chemical reactions called the Calvin cycle.

Photosynthesis can be represented by the following equation: 
6CO2 + 12H2O + light energy = C6H12O6 + 6O2 + 6H2O

This equation basically means that carbon dioxide plus water plus light energy in photosynthesis react to produce glucose and oxygen.

Photosynthesis is vital for life on Earth. For photosynthetic organisms, it is the primary source of energy. All the oxygen in the Earth's atmosphere is produced as a byproduct of photosynthesis, which is critical for the survival of animals as well.

Photosynthesis also impacts the global carbon cycle by acting as a carbon sink—absorbing more carbon dioxide than it releases. This has important implications for climate change. The study of photosynthesis, its mechanisms, and its efficiency, is a significant topic in the field of plant biology.
  
Chlorophyll, which is necessary for photosynthesis, is directly responsible for the green color of leaves. Chlorophyll absorbs most of the sun's colors efficiently but does not absorb green light well, so the light is reflected back to our eyes and the leaves appear green.
