Get one. (I'm just lightly touching the topic here)
A narrowband o2 sensor outputs 14.7:1 as .85-.20volts. Since the ECU idles at 14.7:1 AFR it makes small adjustments to make sure the voltage is within that range. Hooked up to a gauge you will see it sweeping back and forth as those adjustments being made, bouncing to each voltage and back to the opposite. Since it's such a wide range.
The wideband o2 sensor outputs the o2 readings in the exhaust on a linear scale, so at each voltage increment, it represent a new AFR, when outputted to a gauge, you can see exactly the correct mixture of o2 in the exhaust.
so lets assume you have a typical 20 LED gauge, and they are incrementing in a .5v scale. 1v = 9:1 0v = 18:1
Your WB gauge will show you this:
Your NB gauge will show you something closer to this:
notice how Stoich really means stoich