Undoubtedly martial arts existed in China for centuries but it wasn't until the 16th century that reference is made to the kind of organized schools and systems that we think of today as being normal. The earliest known mention of fighting is from the 5th century BCE where an unarmed combat theory is mentioned in the Spring and Autumn Annals. A complete system, called Jueli, existed in the 1st century BCE and this incorporated strikes, throws, locks and pressure point attacks. Over the centuries this art developed into a wrestling sport which was distinct from battlefield and no-holds barred fighting.
Kung Fu and the Shaolin Temple
China is of course most famous for the Shaolin Temple, from which various styles seek to claim their ancestry and therefore greater legitimacy. Legend tells that Bodhidharma, the founder of Ch'an / Zen Buddhism, taught a series of calisthenics to the monks at the temple which had a fighting application. There is no current evidence to support this, though it is recorded that the Shaolin monks twice participated in small skirmishes: in 610 CE to defend against bandits and in 621 CE at the Battle of Hulao. For the next several centuries the monks appear to have lived in peace but from the 16th to 17th centuries numerous records indicate that they were once again engaged in the practice of fighting arts. It is from this period that the legend concerning Bodhidharma was created and the text attributed to him - the Muscle Change Classic - was written (1624).
The greatest period in the expansion and popular participation in Kung Fu came in the first half of the twentieth century. Arts such as Bagua, Eagle Claw,Xing I, Praying Mantis, Tai Chi, White Crane and Wing Chun rose to prominence and were supported by a wealth of training manuals. This growth, at least in China, was short lived and came to be stifled under Communist rule through concern the schools may encourage subversive behavior. It was the masters who escaped the mainland and began a new life in places like Taiwan and Hong Kong who would bring the arts to a Western student body.
Training in Kung Fu tends to be less regimented that in Japanese and Korean arts with classes being more informal. Basic techniques and stances are practiced repetitively and a fundamental aspect is the focus on developing chi / qi, whether the school is internal or external. Chinese martial arts are also heavy on weapons practice and a diverse range of sometimes odd-looking weapons may be studied.