In the article, capacitance is defined as the “build-up of an electrical charge between two conductors,” and it is used in relationship to the way the human finger can move along the arc scroll wheel of an iPod and make the wheel scroll in one direction and then the other. This is possible because the finger is a conductor of electricity, and so is the grid of metal channels beneath the plastic of the scroll wheel cover. The scroll wheel works by having your finger conduct electricity on the other side the non-conductive scroll wheel cover, causing the greatest build up of electrical charge at a particular spot on the grid below the scroll wheel, which can be turned in a precise location. The direction of the locations as you move across the scroll wheel allows the interface on the iPod to, well, scroll through menu options or songs.
The most impressive thing about the word capacitance is that it can easily be compared to popular notions poetry or art or philosophical thought. Think about it: capacitance requires that the two electricial conductors never meet. Otherwise, it is not capacitance. Imagine two forces that strain to touch one another but are prevented from doing so by an immutable obstacle. And it is precisely this obstacle than makes these two conductors two different conductors. Otherwise, they would be a circuit.
They are hopelessly eternally separated, but it is through that separation that they provide something meanful to the rest of us.