[right beside]

Thanks again. I do understand how midi, audio, aux, and instrument tracks work. I understand what you are saying.
When I said : "they insert them on instrument tracks and feed midi through them", I meant to simply say: they feed midi through 'the instrument track' with a virtual instrument instantiated to read the midi and create the audio. then they insert the AIR plugin on that instrument track to attenuate the signal. But what I don't see in the video is whether or not the AIR plugin has its own insert slot or is part of the virtual instrument somehow. That would've cleared things up.
So I asked in the first post: "Also, can the AIR plug-ins be used on audio tracks, or are they for midi/instrument tracks only?", meaning: are they independent plugins usable on all kinds of tracks, or do they only apply to AIR virtual instruments, like the effects within say, reason, or sampletank. Those cant be separated from their host programs and used on other tracks but only within the virtual instrument environment.