Photosynthesis is a process used by plants, algae and some bacteria to convert sunlight into chemical energy. It involves taking in carbon dioxide (CO2) from the atmosphere and water (H2O) from the soil, then using the energy of sunlight to turn these raw materials into glucose or other sugars - which serve as food for the plant - and oxygen, which is released back into the air. In essence, photosynthesis allows plants to create their own fuel while also providing a vital source of oxygen for animals and humans alike.