The phases of the Moon correspond fairly well with the month: about 1 full complete lunar cycle every month. This is by design: the ancients when designing the calendar designed the month to follow the cycle of the Moon. (Even our word, month, comes from the word Moon).
The average lunar cycle lasts 29 days, 12 hours and 44 minutes. It is caused by the fact that, as the Moon orbits around the Earth, the light of the Sun is hitting it at different angles. There is always light hitting the moon, however we are not always able to see it.
During the new Moon, the Moon lies between Earth and the Sun. We are unable to see the light reflecting off of the Moon because it is reflecting away from us, the side of the Moon we see is in darkness.
When the Moon is full, we are in between the Moon and the Sun. We are able to see the full light reflecting from the Moon.
The lunar cycle is separated into four phases or quarters:
New Moon Beginning of the cycle, Moon is not visible.
Waxing Crescent Moon As Moon revolves, a crescent of light is seen growing from the right side.
First Quarter At the first quarter the Moon is half full.
Waxing Gibbous During this time the Moon is growing ever more and more full, the darkness receding to the left side of the Moon.
Full Moon Half way through the lunar cycle, the full light of the Moon is visible.
Waning Gibbous The Moon now begins to grow darker with each passing day, the darkness approaching from the right.
Last Quarter At the last quarter Moon it is once again half full.
Waning Crescent The light of the Moon is now dwindling until it is almost completely dark, starting the cycle again.
You might think that the full Moon is the best time for Moon gazing, however this assumption is incorrect. The best time to watch the Moon is during the first and last quarters of the cycle.
At these times, sunlight is hitting the Moon at sharp angles, providing the deepest shadows on the Moon’s craters and other formations. This provides the sharpest definition for the many amazing features of the Moon, in detail that cannot be seen during the full Moon. It is best to look at the edge of where the Moon becomes light from the darkness, as this will provide the sharpest shadows for your viewing.