On the other hand, a VST piano can either go by using physical modeling (Model the physical properties of the instrument, and calculate how it'd sound) or synthesizing (This type generates a waveform (Sine, Saw, Square wave, etc.) and combine them, and then routing to the filter section for subtraction and addition of frequency and other effects to result in a distinct waveform that represents the sound that you are imitating. The difference between using a Kontakt Piano Instrument and a VST piano is that Kontakt is a sampler, which means Kontakt Library manufacturers can create digital instruments by using audio they've recorded (for example, a Kontakt Piano instrument manufacturer would sample the entire note on a physical keyboard for a different level of velocity qualities of attack, and more advance effects to get a similar tone of the real piano instrument, so, in most case, you won't notice much difference between them).
