What do the arcs on a Smith chart represent?

The grid of a Smith chart is made up of two main families of lines used to plot complex impedances. The complete circles, which all touch the far right side of the chart, represent points with constant resistance. The curves or arcs that radiate from the right side and sweep upwards and downwards represent points with constant reactance. The upper half of the chart contains arcs for positive (inductive) reactance, while the lower half contains arcs for negative (capacitive) reactance.