Wideband is able to read a 'wide' range of AFR's but a narrowband is designed to work it a 'narrow' band of AFR. A narrowband basically just reads about a 1 point AFR range, as this is only as much as is needed to keep a lean cruise AFR. The ECU only needs to add fuel if it is above this range, or take fuel if it is below this range till it gets within the region that the narrowband will read. Or at least this is how I understand it
widebands will work on a larger range. Its the sensor that is the wideband part. The gauge/controller is basically just reading signal from the sensor.
AEM UEGO's dont ever need to be calibrated, Innovates require fresh air calibration every 3 months (recommended at least) from memory. Have absoloutly no complaints about my AEM kit, and there not overly expensive at the moment