Kung Fu and other Chinese martial arts are oftentimes distinguished, in a general way, as being associated with one of two major temples: Shaolin or Wudang. The Shaolin temple, located in the Song Mountains of Henan Province, has become known as the home of the "northern" tradition of "external martial arts." The Wudang temple, located in the Wudang Mountains of Hubei Province (just south of Henan Province), has become known as the home of the "southern" tradition of "internal martial arts."
Now of course any martial arts form includes both "internal" and "external" aspects. In other words, included in any form are both movements and/or postures (the "external" part) as well as certain ways of using mind, breath and energy (the "internal" part). So the distinction between the Shaolin and Wudang forms is, in a way, simply one of emphasis. That said, the origins and differences between the two general styles of practice is worth noting.
The Shaolin martial traditions are rooted largely in Ch'an (Zen) Buddhism -- the form of Buddhism originated by Bodhidharma, a Buddhist monk who in the 6th century AD traveled from India to China. The Wudang traditions, on the other hand, trace their ancestry back to the semi-legendary Taoist priest/hermit Zhang San Feng, and so are rooted primarily in Taoism. Historically, Buddhism and Taoism in China influenced each other in many ways, so once again this is simply a difference in emphasis. In reality, one can usually find both Buddhist and Taoist resonances within any given Chinese martial art form.
The Shaolin martial arts forms have come to be associated with the development of almost super-human physical capacities, which are utilized then in actual combat situations, e.g. in battles with those attacking ones monastery, or -- more commonly today - in martial arts competitions. The Wudang forms are known for their emphasis on the cultivation of heart/mind/spirit and energy -- with the graceful, flowing physical forms simply a means to support or an expression of what is essentially spiritual cultivation.
But again, it really is only a matter of emphasis. The masters of any martial arts form -- Shaolin or Wudang -- will have cultivated great facility in both its internal and external facets, coming to understand all the ways in which body, mind and spirit are intimately inter-connected.
Practitioners of both Shaolin and Wudang forms often utilize knowledge of the pressure-points and acupuncture meridians of Chinese Medicine, and -- in treating injuries -- avail themselves of the lineaments and internal formulas of Chinese herbal medicine.