When the Moon orbits around the Earth and the Earth orbits around the Sun, the angle between the Sun, Moon and Earth changes.  As a result, the amount of sunlight that reflects off the Moon changes everyday. This is called the Lunar Cycle, which consists of 4 primary Moon Phases: New Moon, First Quarter, Full Moon and the Last Quarter.  There are also secondary phases known as Waxing Crescent, Waxing Gibbous, Waning Gibbous and Waning Crescent. All these phases correlate to the "Moon's Age" which is how many days it's been since the last New Moon. Fun Fact: The Moon is approximately 4.5 billion years old. Show off your favorite Moon Phase with this illuminating ring.