The term "full moon" refers to the phase when a celestial body, such as the Moon or other planets in our solar system, is completely illuminated by the Sun as seen from Earth. This means that the side facing us is fully lit and appears bright and round, while the opposite side remains dark. The full moon occurs twice during each lunar cycle - once when the Moon is on its way to becoming full, and again when it's on its way back down after reaching its peak illumination.