The first half of the moon month the light fills the moon (waxing moon) and second half of the moon month the shadow covers the moon (waning moon). At full moon the moon is completely filled with light and at new moon the moon is completely covered with shadow. At first quarter the right half of the moon is filled with light and at last quarter the left half of the moon is filled with light.
keywords: moon cycle, moon phases, yin yang, light and shadow