In honor of the supermoon that'll be visible on April 7, try making (tasty) models of the moon phases!
Why does the moon have phases? As the moon orbits Earth, Earth orbits our Sun at the same time. While we watch from Earth, the moon reflects the light given off by the Sun, as the moon doesn't make any light of its own. The moon continues to orbit Earth, and we see different amounts of the moon lit up depending on our positions. When the moon is full (all the frosting on the oreo is there), the side that is facing Earth is fully lit up by the Sun's light. This is why the complete circle is visible. Over the course of almost 30 days, the moon goes through all the phases we looked at, and then starts back up all over again.