What does “Gong功” mean? Translated simply, it means “Work”, however let’s look at the Chinese character for Gong. It is made of two parts. One part 工 Gong, same pronunciation, means work. This is only work and includes any kind of works. The other part is力, pronunciates “ Li “and this means “Strength”. By strength we do not mean just physical strength but mental as well. So the two parts together mean that Gong is the kind of work that requires skill.
Often we hear the term Kung Fu or Gong Fu功夫. This Kung/Gong is the same character and so together with them mean to work with skill. “Fu夫 “means “Man”, so all together it means a man with skill. This is Kung Fu and it needs skill which takes time to develop. So someone who has any kind of good skill we say they have good Kung Fu. It does not necessarily mean martial arts. It can be skill in cooking, driving or any kind of skill that is impressive. This is good Kung Fu.
Gong together with Qi is Qigong氣功. It means that the Qi needs work, which require skill. So if we want more Qi we need to work on it. This is Qigong.