The shape of the Moon changes throughout the lunar month. The period in which the new moon grows to a full moon and back to another new moon is known as a lunar month.
A lunar month is characterized by waxing and waning. Waxing occurs between the new moon and full moon, when the moon grows in size. The side of the Moon illuminated by the sunlight becomes bigger; it grows from a waxing crescent to waxing gibbous and then to full moon. During the gibbous phase, 51-99 per cent of the moon’s surface is illuminated.
On the other hand, waning occurs between the full moon and new moon. When the Moon is waning, its surface illuminated by the sunlight decreases day-by-day. The Moon changes from full moon to the waning gibbous phase. It then changes to the waning crescent and finally the new moon.
Picture Credit : Google