Astrology can be understood as a philosophy that helps to explain life, rather than a type of mysticism that can be used as a predictive tool. Instead of discussing what the Planets do to us, we can explain ourselves based on Planetary indications.
The Signs work the same way: Each of the twelve Signs is a unique combination of one of the four Elements and one of the three Qualities. The Elements and Qualities demonstrate that we are all part of the environment. There is a connection between all living things and all matter on this Planet.
Astrology ties humans together: We are all faced with the same Planetary interactions, and we are all part of the same cycles.
Tropical Astrology assigns the 12 zodiac signs (each consisting of 30 degrees) based on their position in relation to the Spring Equinox, which marks the Astrological New Year and usually falls on March 21. The Equinox represents 0 degrees Aries.
Sidereal Astrology (found mostly in India) assigns positions based on constellations, rather than in relation to the Equinox. It acknowledges the precession* and adjusts the signs of the zodiac accordingly.
At present, Sidereal Astrology is 24 degrees behind Tropical Astrology, so a person born under 23 degrees Libra in Tropical Astrology is born at 29 degrees Virgo in Sidereal Astrology.