Why does the Moon have different phases?

The Moon is constantly rotating around the Earth, while the Earth is orbiting the Sun. These two factors are the reason that we see Moon phases from the Earth.

Each Moon phase is determined by the relative position of the Moon, the Earth and the Sun altogether. The observer on Earth sees each Moon phase as sunlight reflected from the Moon. For example if the Sun and the Moon are located on the opposite sides of Earth we see the black Moon, since in this situation no sunlight is reflected from the Moon at all. On another occasion the Sun is below the horizon and the Moon is up in the sky, so we see a sickle shaped Moon. Sometimes we even see the Earth's shadow on the surface of the Moon.

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