Well, qi as a
concept is context-dependent.
- TCM types use the concept to describe both general and specific physical functioning. The concept is a tool, sort of a metaphor.
- martial types who know what they're doing use the concept in contrast to li, muscular force. It is a concept that describes unified, distributed force through as much of the body (muscles, bones, tendons) as possible, rather than through specific muscles such as the triceps. This idea of unity and big-picture is woven into the Chinese (and other Far Eastern) culture, while Western culture has emphasized drilling down into components.
- when they talk about moving qi around, they're not talking about some kind of thing moving; they're talking about your mental intention (yi) and internal awareness moving through your body, and if you are practiced enough, this subtle intention can result in slightly increased body functions (e.g. increased circulation) along the way. If you doubt the effects of such movement, think about how signals travel from your brain to your bicep to lift a weight.
- qi as a concept also describes information within the body. It's not numbers or words: those are systems of symbols we've made up. No, the body passes information all the time from your brain to your organs, between your muscles and tendons, telling other components to send more white corpuscles, to pump more blood, whatever. The systems in your body are not isolated: ****'s moving around all the time, and qi is a concept that describes that movement.
- along those lines, this is why some describe the concept of qi as a wave. In a water wave, while the wave seems to move across to our eye, the water just goes up and down if we look carefully. In the sense of qi, something happens at one point in the body and a signal, electrical or chemical happens. That triggers the same thing to happen in an adjacent cell (or whatever), and so on. Nothing actually moves, but this on/off is transferred along a path in the same way that the up/down of a wave occurs. In a metaphorical sense, qi "moves" like a wave "moves."
In a Chinese context, qi is not a thing. It's not measured. It's not electricity. It can't make you do magic.
Chinese types who know what they're doing know that the magical stuff is BS, but they are hesitant to call out the charlatans. Yes, "face" is real. They also don't spell out what I'm saying because from their point of view, it might be patronizing to the Western folk: of course it's a concept, a metaphor. They're trying to save
our face. It would be like our meeting a client who thinks that Sherlock Holmes is a real man. What would we say to him?
It's a useful
concept to describe complex stuff.
It
manifests in measurable phenomena such as increased blood circulation, muscular activity, body heat, but in a TCM context, qi is a
concept that attempts to describe an aggregate of these bodily functions.
In a martial context, it refers to the distributed use of the body components in the application of force or techniques: if you are "using your qi," you have distributed your effort through so many body components, and you cannot easily name which muscles you use to execute a technique. It feels nearly effortless because the effort is distributed through your entire body. Lift a weight with one arm; lift it with two arms, and it weighs half. Extrapolate this concept to shoving someone using only your triceps, then using your entire body. That's "using your qi." Again ignore the charlatans.
I hope that helps.