The Moon orbits Earth once about every 27, days.
But a complete cycle of the Moon’s phases takes about 29 days. This is because at the same time the Moon orbits Earth, Earth orbits the Sun at a different rate, taking the Moon along with it.
So, when the Moon has finished one revolution, the Sun is in a different place from where it was when the Moon began its revolution.
It takes the Moon almost two extra days to reach its cycle’s starting position in relation to the Sun.