The sensor compares reference air and it's oxygen on the outside of the sensor (usually admitted along the wires) to the oxygen level present in the exhaust stream. Voltage is generated depending on the difference between the two.
So it's oxygen, and nothing else, that drives the sensor to produce a voltage, interpreted by the computer as fuel/air ratio, which is adjustable over a fairly narrow band.
I like Wikipedia a lot, but it's not perfect, and sometimes downright misleading.