Your Moon sign represents the part of you that is hidden in your subconscious. The Moon is the feminine archetype in your chart which can influence a lot of your behavior unconsciously.
For example, you might be an outgoing and extroverted Aries, but if your Moon is in a water sign such as Scorpio, there will always be a part of you that you like to keep hidden away from others.
How well your Moon is aspected, as in how it is playing with the other planets in your chart, can also determine the quality of your emotional life; and show what kind of relationship you had to the first and most important woman in your life — your mother (in some charts the Moon also shows the relationship to the primary female caregiver in one’s childhood, which could be a grandmother, or in some cases the father if he was the primary nurturing figure).
This relationship and the subconscious messages you received from your mother, molds your inner nature, your intuition and ability to give and receive nurturing love. For example, a challengingly placed Moon in the chart can indicate that the child in you never received the unconditional acceptance that one expects from their mom. In the case of a man, this can create difficulty in his relationships with the opposite sex, because unconsciously he will feel a lack of safety and trust with them.
On the other hand, a well aspected Moon in the chart can indicate that the person is quite well adjusted emotionally, having received the needed love and support from the mother figure in their lives. In such cases, they are likely to experience much more grace and ease in emotionally intimate relationships than those from the previous example.
Those with strong Moon placements in their charts can also exhibit high levels of intuition, creativity and sometimes be out in the limelight with the public (the Moon creates reflections or projections, so lunar people find it easy to project their images onto the public at times).
Such is the influence of the Moon in your chart.