The history of Chinese martial arts (known in Mandarin as wushu) and most commonly called kung fu or gung fu is centuries old. Developed for self defense and self preservation via mind, body and spirit unification, kung fu has grown into literally hundreds of styles, of which about only two dozen are recognized as being traditional, meaning they have kept the true essence of the style from its origin.
A traditional style must include striking with hands and legs, weapons training, chin na (joint locking, seizing and controlling, pressure points) and shuai chiao (throwing, wrestling). Chinese Kung fu can be categorized by families (jia), sects (pai) or schools (men) of martial arts. Each style has its own brand of physical movements based on the imitation of animals and or philosophies, namely Buddhism and Taoism.
The area in China where a style was founded and developed also plays a part in its classification. A style founded in the southern part of China where the topography is generally flat and situated near large bodies of water, will emphasize low stances and circular movements. In the north, where the land is more mountainous and hilly, a style would show longer and straighter movements. Most styles of Kung fu train the muscles and cardiovascular aspects of movement through strength and speed, these are known as external styles from the Shao'lin school, some examples are: Choy Li Fut, Fu Jow Pai and Wing Chun.
Along with developing the physical aspects of the body, all styles of Kung fu to some extent train the bodies life force known as "chi". There are a few styles that emphasize the cultivation and manipulation of chi more than most, they are known as internal styles from the Wudang school, a few examples are: Tai Chi, Hsing-I and Ba Gua.