Here's a breakdown:

* Photosynthesis takes in carbon dioxide and water, using sunlight energy to produce glucose (sugar) and oxygen.

* Cellular respiration breaks down glucose and uses oxygen to release energy (ATP), producing carbon dioxide and water as byproducts.

Essentially, photosynthesis builds complex molecules (glucose) from simple ones, storing energy, while cellular respiration breaks down complex molecules, releasing energy. They are complementary processes that sustain life on Earth.