What is the phenomenon of "New Moon Embracing Old Moon"?

The new moon holding the old moon, also called the reflection of the earth, is one of the rare astronomical wonders in the world. This scene was shot by Laurent Laveder, an astrophotographer at Pic du Midi Observatory. The dark gray light faintly visible in the crescent arm is actually the sunlight reflected from the earth to the moon and then back.

Careful observation of Canyue reveals that the moon is not completely black except for the illuminated crescent part, but emits grayish yellow light, just like the crescent moon embracing the faint "gray light". People call this phenomenon "the new moon embraces the old moon".

Extended data:

The moon can not only reflect sunlight to illuminate the earth, but also the earth can reflect sunlight to illuminate the moon. Gray light means that the earth has the right to reflect sunlight to the surface of the moon and then back to the ground.

The color of gray light will also change: when the vast ocean part of the earth faces the moon, the gray light is light blue; When the continental part of the earth faces the moon, the gray light turns pale yellow.