The zodiac is like a coordinate system; a map for the sky. The psychic zodiac is also a metaphysical system, one of the oldest ones, and forms the basis of psychic astrology.
The Earth revolves around the Sun, but to us it seems like the Sun is revolving around the Earth. The path of the Sun in the sky can be divided into 12 zones, and these zones form the zodiac.
The modern western zodiac has 12 signs: Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio, Sagittarius, Capricorn, Aquarius, Pisces. Each of these zones corresponds to a 30° piece of the sky (out of the full 360°).
Thousands of years ago these zones corresponded to their respective astronomical constellations, but they are no longer in the same positions they were in then. Astrologers debate whether they should make horoscopes based on the zodiac zones or the zodiac constellations - the first group is more numerous.
From a psychic's standpoint, the Sun is closer than other stars and presents the greatest influence. Any influence of other celestial entities is overshadowed by the Sun's comprehensive and permeating influence which has to be taken into consideration at all times.