I was hoping someone could explain what Fuel Trim bank 1 and bank 2 is? Read on before you just give me a definition.

So I'm using Torque Pro, great app but I noticed we have short term fuel trims and long term fuel trims on each bank like all cars. Nothing needs explained here, I understand the 2. Than we have readings of front and rear 02 sensors. Rears only making sure the cats are functioning. Nothing needs explained here. This is an 03 model by the way.

Over time I've studied fuel trims and tuning, etc etc. Nothing has ever referenced having 3 different fuel trims. Everything is referring to short and long term fuel trims, 02 sensors, narrowband or wideband. So what is this 3rd fuel trim titled Fuel Trim Bank 1 and Fuel Trim Bank 2. I'll copy in a picture in this thread from Torque. As you can see from the pic below we have 3 fuel trims on each bank.

FYI - All 3 fuel trims on each bank are always different, so that's why it's confused me on what it is or what it's purpose is?