As seen in the sky from here on Earth, at the instant when the Moon is 90° west of the Sun, it is at the phase. At that time, it looks like exactly of the Moon is lit up.

The Moon's morphing forms observed from Earth are known as the phases. The Moon only shines when it reflects the light from the sun due to the fact that our moon does not produce its own light.  The Moon's phases are a result of the Moon, Earth, and Sun's shifting locations.

Many civilizations all around the world place great importance on the Moon's phases. For instance, many farmers sow and harvest their crops in accordance with the phases of the moon. In order to determine spiritual celebrations and holidays, the Moon phases are also employed.