Qigong is made up of two words “Qi” and ‘Gong”. An incomplete definition of qi is “energy”.
Qi is invisible to most people, and it has for the most part been difficult to detect it using current detection instruments. When detected, qi shows up as electromagnetic waves, heat, particle flows or a force that propels other visible matter. When a person can actually feel qi in his body, he can feel a full range of sensations from tingling to imaginary ants crawling on the skin.
Many martial artists disdain Chinese kungfu or Japanese martial arts based on qi (or ki in Japanese), such as Aikido, saying qi cannot be seen. But to practitioners of genuine qigong or the internal arts, qi is as natural as life, and many would agree that qi is essential for life. Just because something cannot be seen with the naked eye or even scientific equipment does not mean it is not there. It may simply mean that the human body or the equipment has its limitations. The atom is not visible to the human eye or conventional microscopes. In fact, the atom was not even seen until a mere hundred years ago.
Qi is essentially the stuff which everything in the known universe is made from, from the tiniest particle to the vastness of space, including you and I.
As my teacher succinctly puts it:
“Chi” is simply the Chinese term for energy. There is nothing mystical or mysterious about it. People in both the East and the West have knowledge of energy, except that the knowledge in the East is more profound. This does not contradict my earlier statement that if you tried to explain chi to your friends, they would not understand you. The problem lies not with the complexity of chi, but with your friends’ lack of understanding.
If you tell your friends that chi is necessary for life, they would not understand you because they do not know what chi is. But if you tell them that energy is necessary for life, they would have no difficulty understanding.”
“Gong” is often mistranslated as “work” or “effort” by those who rely on bilingual dictionaries but have no idea of the cultural context of the words they translate.
“Gong” is provisionally translated here as “force”. Actually “gong” is much more than what the term “force” can suggest, but there is no suitable English term that can convey the complete concept of “gong”, and “force” is the nearest equivalent available, though it is in fact still very far off. The whole idea of kungfu (spelt as “gongfu” in Romanized Chinese) is the training and application of “gong”.
Besides force, “gong” includes aspects like accuracy of form, speed, fluidity of movement, temperament, mental clarity and freshness, spontaneity of reaction, and quick decision making. In some ways “skills” many be a better substitute than “force” for “gong”. but it may sometimes give a wrong connotation.
(Reference: https://shaolin.org/answers/sp-issues/horse-stance/fundamental.htmll