The main effects of precession and nutation

The moon goes around the earth. Under the influence of the moon's gravity, the earth's orbit around the sun changes with the period of revolution of the moon. The time difference between the tropic year and the sidereal year caused by the differential rotation of the earth is called precession, while the periodic motion of the earth swinging from side to side in the orbit of revolution is called nutation. Precession causes solar terms to move westward, and nutation causes the position of moon stars to change periodically in our field of vision.