Why A Smith chart is a plot of the complex reflection coefficient overlaid with two families of curves from the normalized impedance grid. The complete circles are the constant-resistance family, and the arcs that branch off the outer edge and converge on the right-hand point are the constant-reactance family. Reading where a point falls tells you R + jX at once: which circle gives resistance, which arc gives reactance. Arcs above the centerline are inductive (+jX), those below are capacitive (-jX).