The sun shines all the time. When it shines, energy is streaming down to Earth. Some of that energy lands on plants. And just about all plants have something called chloroplasts. Plants and animals then use the glucose for food and energy.
Animals use the oxygen to breathe.
It's like having a stack of pancakes floating around inside the chloroplast. Attached to the stacks you can find a molecule called chlorophyll. Chlorophyll sticks to the outside of the thykaloid. Chlorophyll is the molecule that takes the sun's energy and makes sugars. It's a big word that just means connections across the stroma.