The Moon orbits the Earth. Many astrologers consider the Moon as important as the Sun in a person's birth chart. The Moon rules the sign of Cancer. It changes signs every 2 and half days.
The Moon signifies security, our instincts, rest, and nurturance. In a birth chart, wherever the Moon is located is where the person has emotional intimacy and feels the most emotionally comfortable. For example, if the Moon is in the 3rd house, the person will usually have a need to talk about their feelings. The Moon in the 6th house can indicate a need to serve others.
In astrology, many also say the Moon symbolizes the archetype of the mother. It is also known for being moody, subjective, and responsive.
If the Moon is square or in opposition with the Sun, it can lead to difficult emotional states. If the Moon is in conjunction with the Ascendant, it can lead to the person being protective and nurturing.