The Tao
A large part of Taoism has to do with the Tao, or, the life force of the universe, or the way of nature. They believe that suffering and unhappiness happen when people live their lives against the Tao. To become one with the Tao, to live a life of peace and harmony, is the goal of the Taoist. But, despite all of the need for harmony with the Tao, it is not considered a god, and not even worshipped. In fact, as many who study Taoism are surprised to find that they do not have gods in the way that Abrahamic religions do. There doesn't even seem to be a place for gods in the Taoist thinking. But they do have three deities that some branches of Taoism worship. The Three Pure Ones.
The Three Pure Ones
The Three Pure Ones are said to have been created by the Tao himself. The Tao was said to embodied in another being, and when he created the first of the there he was the Great Primordial Being. There are many stories regarding the Three Pure Ones, but the most widely accepted theory is that The Great Primordial Being created Yu-ch'ing (Jade Pure), the first of the three. Then, Shang-ch'ing (Upper Pure), the second of the three, was created by Yu-ch'ing. Then the third, T'ai-ch'ing (Great Pure), was created by Shang-ch'ing. Then, as the final part of the story goes, T'ai-ch'ing created everything else. But in the simplified version of the story, One created Two, Two created Three, and Three created everything else. Three has also been known as the two forces constantly at work in the universe, yin and yang.
Yin and Yang
Taoists believe that there are two major forces constantly at work in the universe, yin and yang. These forces are believed to be constantly at work and need to be kept in balance. Yin is a cool, dark, soft, and feminine force often seen in snow, clouds, and rain. Yang is a hot, bright masculine force, seen in thunder or the sun. These are one of the strongest beliefs in Taoism, but they are not the main energy for them, people do not try to harness the yin if they are female, or the yang if they are masculine, everybody tries to harness their chi, or life-breath of the universe.
Chi
Chi is believed to be the life-breath of the universe. It is within and around each person. People are born with all the chi they will need for their lifetimes. Often, people will do exercises to help preserve their chi, therefore extending their lifetimes.