There are three main branches of astrology, namely Western astrology, Indian astrology, and Chinese or East Asian astrology. The study of Western astrology and the belief in it, as part of astronomy, is first found in a developed form among the ancient Babylonians; and directly or indirectly through the Babylonians, it spread to other nations. It came to Greece about the middle of the 4th century B.C., reached Rome before the advent of the Christian era.

With the introduction of Greek culture into Egypt, both astronomy and astrology were cultivated in the Nile region during the Hellenistic and Roman periods. Astrology was further developed by the Arabs from the 7th to the 13th century , and in the Europe of the 14th and 15th centuries astrologers were dominating influences at court. The Mayans of Central America and the Aztecs also developed their own form of astrology.

The terms astrology and astronomy have long been closely related. An Astrologer is an interpreter of celestial phenomena, while an Astronomer is a predictor of celestial phenomena. Astrology itself can be divided into two camps: "Natural astrologers" (i.e. astronomers) study the motions of the heavenly bodies, timing of eclipses, etc. "Judicial astrologers" study the supposed correlations between the positions of various celestial objects and the affairs of human beings.