Why does the moon appear to change shape at different times?

The appearance of the moon changing shape at different times is due to the visibility of the illuminated portion from Earth changing. As the moon orbits around the Earth, the relative positions of the moon, Earth, and the sun result in different portions of the moon being illuminated. This cycle of illumination creates the various phases of the moon, such as new moon, crescent, first quarter, gibbous, and full moon.

As the moon progresses through its orbit, we see varying amounts of the illuminated side, which leads to the observed changes in shape. This phenomenon does not imply any physical change to the moon itself, nor does it involve any alteration to its color. The moon remains a solid body, and it is purely the angle of sunlight reflecting off it, combined with our perspective from Earth, that produces the myriad of shapes we observe.