The lunar cycle lasts slightly over 27 Earth days, or the same amount of time it takes the moon to complete one orbit around the Earth and complete one lunar day. The phases of the lunar cycle change based upon the moon's location along its orbit.
The lunar cycle has eight distinct phases. When the moon is not visible from the Earth, it is undergoing a new moon phase. As it becomes more visible, it moves through the waxing crescent, first quarter and waxing gibbous phase on its way to becoming a full moon. As it cycles back to a new moon, the moon moves through the waning gibbous, third quarter and waning crescent phases.