Photosynthesis means "putting together with light". It is a manufacturing process that happens within cells of plants and within tiny bodies called chloroplasts. These plastids are located in the cytoplasm of leaves and contains the green coloring matter called chlorophyll.
When photosynthesis takes place, water that has been absorbed by the tree's roots is carried to leaves where it comes in contact with the layers of chlorophyll. At the same time, air, which contains carbon dioxide is taken into leaves via leaf pores and exposed to sun light and a very import chemical reaction occurs. Water is broken down into its oxygen and nitrogen elements, combines with carbon dioxide in the chlorophyll to form sugar.
Another valuable byproduct of this chemical reaction is leftover oxygen the leaf releases back into the atmosphere. That oxygen becomes a part of the air we breath while the glucose is carried to the other parts of the tree as nourishment. Also from this reaction comes 95% of of what becomes the existing tree. Incredibly, out of thin air and water comes the vegetative biological organism called a tree.
Photosynthesis - the English translated chemical equation for this process is:
6 molecules of carbon dioxide + 6 molecules of water + light → glucose + oxygen
Many processes occur in a leaf, but none more important than photosynthesis and the resulting food it manufactures. So, through the works of green plants, the radiant energy of the sun is captured in leaf structure and made available to living things. Except for a few kinds of bacteria, photosynthesis is the only process by which organic compounds are constructed from inorganic substances, with a resultant storage of energy.
Unfortunately, some 80 percent of the earth's total photosynthesis is produced in the ocean and largely unavailable to creatures living on the land. So pressure is constantly on terrestrial plants to keep up the pace. Good news is, the total production of sugar by land plants is estimated to be 40 billion tons a year and much more than enough to support every living terrestrial organism at present.