Here's why:

* Position: During a full moon, the sun and moon are on opposite sides of the Earth. This means the entire sunlit face of the moon is facing Earth, making it bright enough to be seen even during daylight hours.

* Brightness: The full moon is the brightest phase of the moon, reflecting the most sunlight.

While other phases of the moon might be visible during the day, they will be significantly fainter and harder to spot.