Astrology is both a science and an art. As a science, it is based on careful observation of the "zodiac," the astrological name for the heavens high above Earth which include the Sun, the Moon, the starts, and the planets.
Astrologers belive that these heavenly bodies exert a powerful influence on the development of each individual's personality and destiny. The art of astrology lies in the interpretation of these complex celestial influences.
Ancient astrologers divided the zodiac into twelve sections called the astrological signs. As Earth orbits the Sun, it passes through each of these twelve signs in one calendar year. The first sign, Aries, begins at the spring equinox. It is followed, in order, by Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio, Sagittarius, Capricorn, Aquarius, and Pisces. Each sign is dominated or "ruled" by a planet that represents certain traits or talents.
The most important influence on you is your sun sign, which is simply the astrolgical sign on the date of your birth. But there are many others that shape the personality, including the moon sign, the rising sign, and the planetary influences, as well as the four "natural elements" and the three "qualities" established by ancient astrologers.