Final answer:
Zodiac signs are part of astrology, which assigns symbolic meanings to celestial phenomena. While often used for guidance, scientific testing has shown no predictive power in astrology. Zodiac signs remain popular for their psychological and reflective value rather than empirical evidence.
Step-by-step explanation:
The main reason for zodiac signs has to do with astrology, a system that people have used to seek meaning in the sky's influence on earthly events and individual fortunes. When someone asks for your "sign," they typically mean your "sun sign," which refers to the zodiac sign the Sun was located in at the time of your birth. The zodiac itself is a belt in the sky divided into 12 signs, each named after the constellations the Sun passes through over the course of a year. However, due to the precession of the equinoxes, these constellations have shifted over time.
Despite the longstanding human interest in astrology, extensive scientific testing has found no evidence that natal astrology or sun sign predictions hold any predictive power. Astrologers often provide guidance by using the language of the horoscope and zodiac signs more as a tool for reflection, akin to amateur therapy, rather than as a scientifically backed prediction method.