Oh, what a splendid question! The moon is illuminated at night because it reflects the light from the shining sun. As the Earth turns, different parts of the moon appear bright to us down here. Just like how you can always brighten someone's day with a smile!
The appearance of the moon changes from night to night because different parts of the moon are illuminated by sunlight, from the perspective of the viewer here on Earth. The moon itself is not changing, it remains the same.
The moon is illuminated by the sun. It is not luminous, since it emits no light of its own, only reflected light.
When the illuminated portion is decreasing from one night to the next, the moon is in its 'waning' phases.
This phenomenon is known as waxing. The moon is transitioning from a new moon phase to a full moon phase, when more of its surface is illuminated by the sun each night.
When less and less of the illuminated half of the moon can be seen each night, it is called the "waning" phase of the moon. Specifically, this occurs after the full moon, leading to phases such as the waning gibbous and waning crescent. During this time, the visible portion of the moon decreases until it reaches the new moon phase.
The moon. Half moon. OneHalfMoon.
What changes is the part of the Moon that is illuminated. We see the illuminated part of the Moon better than the dark part.
It is illuminated by the Sun, just as Earth is.
The appearance of the moon changes from night to night because different parts of the moon are illuminated by sunlight, from the perspective of the viewer here on Earth. The moon itself is not changing, it remains the same.
When the moon appears as a half-illuminated disk, and the illuminated portion is growing from one night to the next,the phase is known as "first quarter".
The moon is illuminated by the sun. It is not luminous, since it emits no light of its own, only reflected light.
When the illuminated portion is decreasing from one night to the next, the moon is in its 'waning' phases.
The terminator (twilight zone) is a line that delimits the illuminated day side and the dark night side of the Moon.
During the two-weeks' period when the illuminated portion of the moon is increasing from night to night as seen from the earth, we say that the moon is in its "waxing" phases.
This phenomenon is known as waxing. The moon is transitioning from a new moon phase to a full moon phase, when more of its surface is illuminated by the sun each night.
It is not 'called' anything. The moon has not yet risen at your location.
A gibbous moon appears as a large, round shape in the night sky, with more than half of its surface illuminated by the sun.