Photosyntheis is the process used by plants to make their food. With the help of the sun's energy, they make glucose, otherwise known as C6H12O6 out of carbon dioxide (CO2) and water (H2O). The formula is as follows:
6CO2+12H20 ---sunlight and chlorophyll---> C6H12O6, with by-products oxygen and water.
There are parts of a plant that are important to conduct photosynthesis. I'm sure you can be diligent enough to research for that in your sixth grade science notebook.