Characteristic Impedance

This document shares a conceptual insight on the characteristic impedance topic. Last night, I was thinking about a method to explain (in simple words) "characteristic impedance". More particularly, explaining how the characteristic impedance is different than the conventional concept of the impedance. My conclusion was that the best viewpoint to the concept of characteristic impedance is the one that looking through the signal time window, (i.e. traveling / propagating with the signal peak through the circuit). This document, actually, employs a similar method.