Check engine light on!

I have a 1996 Ford Taurus with a 3.0L V-6 and @110,000 miles on it. The check engine light is on, and a scan tool revealed one fault code. It is a P0133 "O2 sensor circuit slow response Bank 1 Sensor 1".
Does anyone know which sensor this is? I know that Bank 1 is the engine bank with the #1 cylinder, but Sensor 1?? Does that mean the Upstream O2 sensor as opposed to the Downstream?
Any help would be appreciated!

upstream

All fords past 1996 have a constant check engine light on, it's quality, done right!