Qin-na are the aspects of Chinese Martial arts that emphasize grappling and locking techniques. These have existed since the beginning of martial practices in China for thousands of years. Qin-na is a part of all Chinese martial arts styles to some degree or another, some emphasize it more and others less whilst some styles have even been built around them.
The advantage of Qin-na is that they allow a practitioner to seize or control an opponent to some degree without needing to severely injure or kill (although Qin-na techniques can be applied lethally if so desired) when compared to striking. For that reason even today much of the military and police force in China are also exposed to basic Qin-na methods.
Qin-na techniques included an infinite number of variations with techniques that leverage an understanding of leverage and kinesiology. Methods include the manipulation or destruction of joints, tendons, muscles and sinews as well integrating those techniques with cavity (triigger points) pressing or sealing of the breath. Thus from the twisting of joints to the tearing/ripping of muscle can all be considered Qin-na.
Qin-na techniques can be applied in combination with general combat and included methods from standing to ground positions accordingly.