This means that the lunar hemisphere facing Earth – the near side – is completely sunlit and appears as a circular disk. This occurs when Earth is located between the Sun and the Moon (more exactly, when the ecliptic longitudes of the Sun and Moon differ by 180°). The full moon is the lunar phase when the Moon appears fully illuminated from Earth's perspective. This full Moon was near its northernmost ecliptic latitude (or northern lunistice), so the southern craters are especially prominent and cast shadows visible from Earth.
The full Moon of 22 October 2010, as seen through a 235 mm (9.25 in) Schmidt-Cassegrain telescope.