As the Moon orbits the Earth, the portion of illuminated Moon that we see changes – giving rise to the phases of the Moon. Starting at the New Moon phase, the Moon appears to expand in illumination.
The Moon has different phases because it depends of the position of the Moon compared to the position of the Earth and also the Sun. The Sun continuely iluminates half of the Moon and the other half is dark. At the same time, the Moon goes around the Earth.
