The phase of the Moon when it is on the same side of the Earth as the Sun is called a New Moon.

Here's why:

* Sun, Earth, and Moon Alignment: During a New Moon, the Sun, Earth, and Moon are aligned in that order. The Moon is positioned between the Earth and the Sun.

* Sunlit Side: The Sun's light illuminates the side of the Moon facing away from Earth. Since the Moon's illuminated side is facing away, we can't see it from Earth.

* Appearance: This results in the Moon appearing completely dark or invisible from Earth.