In addition to being the second luminary of the zodiac, the Moon is the closest celestial body to the earth.  Other than the sun it is the easiest thing in the sky to identify. It is common knowledge that the Moon controls the ebb and flow of the tides on earth. We also see a significant correlation between a full moon and its effects on human population, more specifically the emotions. It is often said that during a full moon there's a spike in criminal activity, as well as more emotional outbursts.

In the zodiac the Moon rules the sign cancer. The moon, as a reflection of the sun, represents our personality and subconscious. It is how we react emotionally to our circumstances. The Moon is our capability for nurturing as it represents the mother in our zodiac chart. The moon is also the natural ruler of the fourth house which represents the home. In the body, it governs the stomach, which is the organ that nourishes.

The Moon is our emotional disposition. Why are some of us more easily embarrassed than others? Why do we get angry, scared, nervous, or sad in certain situations? These are all questions answered by the placement of the moon in your chart. The moon rules our subconscious mind, the passive side to our thought process. 

If the Sun is our character and vitality, showing who we are when we are alone, then the moon is the personality that shines through as a reflection of that light. The moon shows people what we want them to see, as opposed to seeing the true source of who we really are. It is similar to the idea that you cannot look directly into the sun, however, you are able to look directly into the moon seeing the sun's light.