Photosynthesis is the process by which plants, algae, and some bacteria convert light energy into chemical energy in the form of glucose (sugar). This glucose is then used as fuel for the organism's growth and other life processes.

Here's a breakdown:

* Inputs: Carbon dioxide (CO2) from the air, water (H2O) from the soil, and sunlight.

* Output: Glucose (C6H12O6) and oxygen (O2).

So, the primary product of photosynthesis is glucose, which is a type of sugar that serves as the plant's food source. Oxygen is also produced as a byproduct.