VITAL PRESSURE POINTS
Hitting sensitive points, such as the eyes, throat, nose, chin, solar plexus, testicles, knees, or joints in general, has always been considered normal, if it is a matter of life or death. Obviously, agonistic battle has eliminated these techniques, present in all the ancient styles, still visible in many forms, and blows with unconventional parts of hands, like fingers.
Depth studies, for example in disciplines such as Dim mak of Qinna, and then the kyusho jitsu in modern times, have been identified numerous points of the most sensitive human body. All major nerve areas (the concept of the point is often wrong, best to consider areas), but not only, are potential weaknesses of our opponent. They may cause damage of various kinds and intensity. They can, if grasped or pushed, force your opponent to move quickly in the direction we wanted, for example, simply with the pain that we cause by pressing on a nerve.
Obviously to know a sensitive point is one thing, to hit or grab it during a fight or combat is something else. Therefore, it is essential to integrate the learning of vital points with martial arts such as Wing Chun, the kraw Maga, the kung fu, or karate in case of kyusho jitsu.
Obviously they are not techniques from competition use, but in mma, for example, knowing where to press a nerve of an opponent in mounts, perhaps "inadvertently", could free you quickly from opponent, with very little physical effort.
See also: wikipedia pressure points