Answer:
Is a full moon
Step-by-step explanation:
When from the Earth the disc of the moon is complete, it can mention that is the "full moon". In this position, the moon is at the opposite side of the sun, so it looks complete the disc because the light emitted by the sun can be reflected completely by the moon that is in the "dark zone" of the Earth.
When the moon is between the sun and the Earth, the opposite effect is visible, because of the light of the sun, the moon is almost invisible, and from the Earth just a thin line of the moon is visible.