Photography of full moon.
The moon orbits the earth and it looks to us like its shape is changing, but in reality. we look at the illuminated parts of the Moon.
We see the entire illuminated part of the Moon as the Full Moon (the Earth is located between the Sun and the Moon). When the Moon is empty, we see only its unlit part (the Moon is located between the Sun and the Earth.
Image: photography from my LG Q7