Why A Smith chart is drawn in normalized units, where every impedance is divided by the characteristic impedance of the system. The prime center, the point at the middle of the resistance axis, is assigned that reference impedance value (1.0 normalized, typically 50 ohms in amateur work), and all other chart readings scale from it. To get actual impedance, multiply the chart reading by the value you gave the prime center.
Watch out The choices about swapping the resistance and reactance axes describe nothing real: those two axes are fixed features of the chart's coordinate system and are never reassigned to each other.
Normalize = set the prime center to Z0 (usually 50 ohms); the center is always 1.0.