Why is the moon sometimes round and sometimes curved?

The moon is sometimes round and sometimes curved, mainly because the positions of the earth and the moon are changing.

The moon goes around the earth, and the earth goes around the sun. When the earth does not completely block the sunlight shining on the moon during its operation, the moon will appear round, and if it is blocked, it will appear arc. "

The shapes of the moon are new moon, waning moon, first quarter moon, full moon, full moon, waning moon, second quarter moon, second quarter moon and waning moon. The waning moon appears in the western sky at the beginning of the month in the evening, and there will be a sickle-shaped moon. The first quarter moon appears in the first half of the first half of the month. In the western sky, the moon faces west, and the western half of the moon is bright. The full moon, also called the full moon, when the earth is between the sun and the moon, the light of the whole moon faces the earth, and you will see the complete moon. The waning moon appears in the eastern sky at the dawn of the end of the month. The moon faces east and is hooked.