Astrological signs represent twelve equal segments or divisions of the zodiac. According to astrology, celestial phenomena reflect or govern human activity on the principle of "as above, so below", so that the twelve signs are held to represent twelve basic personality types or characteristic modes of expression.
In Western and Asian astrology, the emphasis is on space, and the movement of the Sun, Moon and planets in the sky through each of the zodiac signs. From the viewpoint of earth, the Sun appears to move along a circular orbit across the celestial sphere, this circular orbit is called the ecliptic. The zodiac refers to the thin band along the ecliptic composed of the zodiac signs and constellations.
The zodiac is divided into twelve different signs each of which is 30 degrees long. The order of the zodiac signs is Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio, Sagittarius, Capricorn, Aquarius and Pisces. (With material from: Wikipedia)