Chinese martial arts, also known by the Mandarin Chinese term wushu, and popularly as kung-fu, include a number of fighting styles that have developed over the centuries in China. These fighting styles are often classified according to common features, identified as "families" (jiā), "sects" (pài) or "schools" (mén) of martial arts. Examples of such features include physical exercises that copy certain animals, or training methods inspired by Taoism, and legends. Styles focusing on qi are called "internal" (nèijiāquán), while others concentrate on improving muscle and heart fitness, and are called "external" (wàijiāquán). They are also often classed according to region, that is "northern" (běiquán) and "southern" (nánquán).