A Sung Dynasty statue of Kuan Yin
Some of these gods are representations of the weather or natural forces like the sun or the moon or the rain. For instance, the goddess Ba, the daughter of Heaven, is a personification of drought (she's what drought would look like, if drought were a person). Yu-huang is a sky god, and Fei Lian and Feng Po Po are wind gods. Lei-Kung and Lei-zi are the gods of thunder and lightning. Heng O is the moon goddess. Gong gong is the god of disastrous floods. Han is the god of the Han river - there were many such minor gods, each responsible for a particular river or mountain. Hou Ji is the god of millet, an important food in northern China.
Sometimes people made abstract ideas into gods, like Cai-shen, the god of prosperity, who you could pray to for success in business, for instance. Fan-kui is the god of butchers, and Sun-pi is the god of cobblers (shoe-makers). Fu-xing is the god of happiness, and Gong De Tian is the goddess of luck. Wei-tuo is the god of teaching.
Cheng-huang protects your city from enemies and brings rain for your crops, and help you get to Heaven after you die. Tsao Wang is the god of your hearth, who watches over your house. Every year he reports on how you have behaved and brings you good luck if you have been good and bad luck if you have been bad.
Some gods are based on Taoist ideas, like the eight gods of the Ba Xian (or Pa Hsien), who represent eight ways of being human: being young, being old, being poor, being rich, being a peasant, being an aristocrat, being a boy, and being a girl. (The way these are organized into opposites reflects the Taoist idea of yin and yang).
Other Taoist gods include Bixia Yuanjin, the goddess of dawn and childbirth, and Chu Jiang, a god of the dead in the underworld. Some are based on great victorious generals, actual men who were remembered in this way. Kuan-Ti, the Taoist god of war, was a real general of the Han Dynasty.
Some Chinese gods are great Buddhists of the past, who are now in Heaven. Dha-shi-zhi, for example, broke the cycle of reincarnation with her great love, and now welcomes souls to Heaven in the form of flowers. Di-Cang is a great Buddhist who releases the souls of the dead from the underworld. Kuan-Yin is a goddess of mercy, who helps childless women.
To find out more about ancient Chinese gods, check out these books from Amazon.com or from your library:
The Gods and Goddesses of Ancient China, by Leonard Everett Fisher (2003). For kids. One page for each god, with lots of pictures and some historical context.
Five Heavenly Emperors: Chinese Myths of Creation, by Song Nan Zhang (1994). Stories for kids.
Chinese Mythology A to Z, by Jeremy Roberts (2004).
Dragons and Demons : Myths of China, by Stewart Ross (1998). A few Chinese stories, retold for kids.
Dragons, Gods and Spirits from Chinese Mythology, by Tao Sanders (1983). More of a child's encyclopedia.