There is both martial and non-martial neigong. Well known examples of martial neigong are the various breathing and focus trainings taught in some traditional Taijiquan, Baguazhang and Xingyiquan schools. An example of non-martial neigong is the discipline known as Daoyin.
Neigong and the internal martial arts
The martial art school of neigong emphasises training the coordination of the individual's body with the breath, known has the harmonisation of the inner and outer, 內外合一, creating a basis for a particular school's method of utilising power and technique.
Neigong exercises that are part of the neijia tradition involve cultivating physical stillness and or conscious movement, designed to produce relaxation or releasing of muscular tension combined with special breathing techniques known as the "tortoise" or "reverse" breathing methods to name but a few. The fundamental purpose of this process is to develop a high level of coordination, concentration and technical skill that is known in the martial arts world as 內勁. The ultimate purpose of this practice is for the individual to become at one with heaven or the Dao 天人合一. As Zhuangzi stated, "Heaven, earth and I are born of one, and I am at one with all that exists 天地與我並生, 萬物與我唯一".
Neigong and meditation
This type of practice is said to require concentration and internal reflection which results in a heightened self-awareness that increases over time with continued practice. Neigong practitioners report awareness of the mechanics of their blood circulation, peristalsis, muscular movement, skeletal alignment, balance, etc.
What is said to be occurring as the result of continual practice is a type of internal alchemy, that is a refinement and transmutation of the "Three Treasures" or ''San Bao'' 三寳, in Chinese. The Three Treasures are known as 精, Qi 氣 and 神 and can be loosely translated as Essence, Vitality and Spirit.
According to Daoist doctrine the Three Treasures can be described as three types of energy available to humans. The Dao De Jing purported to be written by Lao zi states in chapter 42 that "The Dao 道 gives birth to the One, the One gives birth to the Two and the Two gives birth to the Three and lastly the Three gives birth to the 10,000 Things ; which is all that exists in heaven and on earth.