The Moon is very much the opposite to the Sun. The Sun gives out light while the Moon is merely a reflector of the light. It has no light of it's own. The Moon effects a number of the daily cycles on the planet such as the ocean tides, a woman's menstrual cycle and the insects that fly by the light of the Moon. Indeed it is debatable whether life could exist on Earth without the Moon.
The Moon acts as an indicator of the levels of energy being expressed by the Sun. It starts of with a new waxing moon, followed by a first quarter moon, followed by a full moon when the energy reaches it's peak, followed by the final quarter waning moon as the energy decreases. The energy shown by a full moon has been statistically observed on the planet to correspond with a higher incidence of crime, dreams, and accidents. Indeeed the word Lunatic derives from the influence of the lunar planet on human nature. Many people say only to begin projects during the waxing Moon cycle as the energy is on the increase during this period.
From the point of view of the Earth the planet that moves the fastest is the Moon. It travels through all of the Zodiac signs in 28 days. Indeed it is the most personal planet to the Earth. Like a constant companion or friend it follows the Earth wherever it is. As the Sun is a Yang type outgoing energy representing the male side , the Moon is a Yin type receiving energy representing the female side. The Moon represents our need to receive the light and energy given out by the Sun. This energy can then be manifest into something tangible in our lives. The Moon is the archetypal mother energy. When we are a child we feel the energy of the Moon very strongly as it quickly moves through each of the Astrological Signs. It's changing influence is reflected in our changing daily emotions as we feel sad or happy depending on whether we get what we need. Are we hungry or satisfied, warm or cold, tired or rested. As such the Moon in a persons chart represents their daily changing emotional nature and needs. It is a persons desire to be nurtured and have their requirements met , to be loved and emotionally cared for. As we grow up this moon energy often gets buried as we move more to expressing ourselves and the Sun energy we contain, to be less reactive. However even as we grow up this inner child still remains the central part of ourselves even as we deal with the day to day realities of the world. Indeed looking after this core part of ourselves is fundamental to our happiness.
As with the Sun the Moon only rules one astrological sign and as such it is doubly powerful in this sign. The Moon rules the sign of Cancer. Cancerians are noted for their emotional nature, their need for security, their love of the home, and their nostalgia for the past. Under the influence of the Moon, much like a child, Cancerians need to feel safe and loved and secure before they can express the many talents they have. Cancerians are directly effected by the energy of the moon and their energy levels move with the waxing and waning moons. Just watch a Cancerian on a full Moon. Cancerians are noted for their care of other people and their abilities around the home. They make some of the best cooks.