A Wideband O2 (oxygen) Sensor is a sensor that you install in your exhaust to measure the Air-Fuel Ratio (AFR) of your engine.  The AFR tells us useful information about the combustion process and is commonly used to tune the fuel maps on a bike.  The Wideband O2 Controller converts the signal from the sensor into an analog 0-5v voltage, which can be logged alongside other engine data allowing you to accurately tune your fuel maps using a Woolich Racing Log Box v3 and the AutoTune feature in the WRT software. 

You will need to purchase BOTH a Wideband O2 Sensor and a Wideband O2 Controller, these are generally sold together as a kit.