Astrological compatibility (synastry) is the branch of astrology that studies relationships by comparing natal horoscopes. A natal horoscope is a chart or map of the angles of the planets in the Solar System and their positions in the zodiac at the exact time of a person's birth. These angles represent the positive and negative relationships between the planets.
These relationships describe the relationship between the two people under consideration. Compatibility between Zodiac signs is always approached within a particular branch of astrological tradition: Western astrology, Vedic astrology or Chinese astrology.