Unlike Western astrology, which bases its major system - the Sun signs - on a 12 month cycle, giving a different influence to each month, Chinese astrology is based on cycles of 60 years. Each year is assigned both one of the 12 animals and one of the five elements - wood, water, air, earth and metal - and so the years are more properly defined as the Year of the Water Tiger, The Year of the Earth Pig and so on - sixty in all.
If your birthday falls in the Year of the Rabbit, you are diplomatic and well-liked. If you were born in the Year of the Rat, you are expressive and quick-witted. Similar kind of statements are there for the Year of the Dog, the Ox, the Tiger, the Dragon, the Snake, the Horse, the Goat, the Monkey, the Rooster and the Pig - but to think that this is all there is to Chinese astrology is as simplistic as believing that you can know everything there is to know about a person if you know that they are a Capricorn.
Western astrology focuses on defining personalities and influences. The purpose of Chinese astrology is more direct - to define 'cures' for unfortunate stars by correcting imbalances in the natal chart. Thus, systems like Feng-Shui use the astrological chart as a starting point to prescribe ways to bring balance into one's life. The concept of balance and of Yin and Yang is one that is vital to every aspect of Chinese astrology. Each animal, each element and each year is either Yin (soft) or Yang (hard).
Obviously, every person born in a particular year doesn't share the exact same fate and personality, any more than every person born under a Western astrological sign does. To refine predictions, Chinese astrology uses a complex system of twelve Palaces, similar to the twelve astrological Houses in Western astrology. Zi Wei Dou Shu is used to create a person's entire astrological chart by assigning each of the 'stars' to a Palace. It is the arrangement of these Palaces and stars that determine the influences that a person must affect in order to affect his fate.
There has been virtually no research in the west on the history of Chinese astrology and therefore Chinese astrology never achieved either the complexity and sophistication, or the dominance as a method of divination, that it did in other countries especially in India