only useful to see if your car is running lambda 1.....
thats pretty much all they are good for
they are a voltage switch essentially that fluctuates between 0-1volt... the relative time it remains and for how long dictate how much the ECU trims the fuel to achieve lambda 1.
0- lean
1 - rich
Widebands run 0-5 volts and are able to read fuelling correctly, there are also several types of wideband... the Innovate type, Bosch sensors are prone to read mildly incorrectly under extreme temps, (this is fine for road use)... but for accurate dyno calibration its best to have a more advanced UEGO sensor that is not so affected by temp, its also faster and can still read fuelling even under misfire conditions.
there are Pseudo widebands that are only 4 wire... these are still switches but offer a reasonable wideband effect sensor... but cant read under misfire or very lean / rich conditions.
Andy