The Moon is only ever half illuminated by the Sun, so just like the Earth, the moon has a light side and a dark side (the day side and the night side). The Moon takes around one month to orbit our planet and is the origin for the word month. From our viewpoint on Earth, as the moon orbits around us we see differing ratios of its dark side and light side. These differing ratios are given names and are know as the phases of the Moon.