The moon rules the public as well. This is because the intuitive nature of the moon helps you to sense what the world around you is feeling.
The sign the moon was in at your birth will help you know how you express your feelings. In an intellectual air sign like Gemini, Libra, or Aquarius, you may have difficulty tuning into your own emotions. However, it can make you quite good at counseling others because you have the ability to detach emotionally. In water signs like Cancer, Scorpio, or Pisces, you may be highly in tune with the emotional undercurrents of life. However, you may need to go off in private to separate your feelings from the emotions of those around you.
Physically, the moon is associated with your digestive system, the disease cancer, and breasts.
If you read your daily horoscope, it would be useful to read your moon sign as an indicator of how your emotions are operating for the day.