Caption: A diagram illustrating how the difference between lunar month (mean value 29.53059 days, (J2000.0 to 7 digits) the sidereal month (mean value 27.32166 days, epoch J2000 to 7 digits) arises.
Features:
It could also be called the synodic period: i.e., orbital period relative to the Sun.
By the time one sidereal month has passed, the Earth has moved eastward along its orbit and the Moon has NOT returned to the new moon position.
It takes the Moon a bit more than two days to get to the new moon position and complete a lunar month.