Here's how:

* Carbon dioxide (CO2) is fixed: The cycle begins with the enzyme RuBisCo incorporating CO2 into a five-carbon sugar called RuBP.

* Energy is used to produce sugar: The fixed carbon is then converted into a three-carbon sugar called G3P using energy from ATP and NADPH (produced in the light-dependent reactions of photosynthesis).

* Regeneration of RuBP: Most of the G3P is used to regenerate RuBP, allowing the cycle to continue.

* Glucose production: A small amount of G3P is used to produce glucose, which is a vital source of energy for the plant.

So, while the Calvin cycle produces G3P directly, it ultimately results in the production of glucose, which is the product that plants use for energy and growth.