A "Moon sign" refers to the zodiac sign that the Moon was in at the time of a person's birth. It is an essential part of astrology, alongside the Sun sign and rising sign. The Moon sign is believed to influence a person's emotions, instincts, and inner self, reflecting how they respond to their feelings and the world around them. To determine one's Moon sign, an astrologer needs the exact date, time, and location of birth. Each of the twelve zodiac signs can represent different emotional traits, such as Cancer for sensitivity or Leo for warmth. Understanding your Moon sign can provide deeper insights into your personality.