At Full Moon, the entire face of the Moon is illuminated by the Sun’s rays and it can be bright enough to light up otherwise dark nights.
Technically, this primary Moon phase only lasts a moment, the instant when the Sun and the Moon are aligned on opposite sides of Earth (see illustration). So the exact time for Full Moon is during the day on parts of the planet.
However, the Moon can appear to be full a day before or after while more than 98% of the Moon’s disc is illuminated.
Therefore, it can be difficult to tell the difference between a Full Moon and the last stage of a Waxing Gibbous Moon or the beginning of a Waning Gibbous Moon.
The technical term for the Full Moon alignment is syzygy of the Sun-Earth-Moon-system.
When the side of the Moon we can see from Earth is fully lit up at Full Moon, the opposite side is in darkness, and vice versa at New Moon.
The Full Moon is visible in the sky approximately from sunset to sunrise. At the precise moment of the Full Moon alignment, the Moon is only visible in the night part of Earth, with a few exceptions.