Astrology is based on the relationship of all celestial bodies to the earth. It is mainly concerned with all the heavenly bodies in our solar system including the planets, the sun, the moon, asteroids and comets. Celestial bodies outside of our solar system, including the stars and constellations are also important. Often referred to as horoscopes, astrologers use the information concerning the planetary movements with that of birth signs to predict certain events. These could be minor events or they could be life-changing.