During which phase is the Moon completely illuminated from Earth's perspective?

The Moon is completely illuminated from Earth's perspective during the Full Moon phase. This occurs when the Earth is positioned between the Sun and the Moon, allowing the Sun's light to fully illuminate the side of the Moon that faces Earth. This results in a bright, round disc in the night sky, which is why the Full Moon is so prominent and easily recognizable.

In contrast, during the New Moon phase, the side of the Moon that is illuminated by sunlight faces away from Earth, making it virtually invisible from our perspective. The Waxing Crescent phase shows only a small sliver of the Moon illuminated as it begins to wax toward fullness. Lastly, the Waning Gibbous phase occurs after the Full Moon, where the illuminated portion is decreasing, but still not complete. Thus, the Full Moon phase is specifically characterized by complete illumination.