Well....I'm going to get blasted for this, but i'm beyond the point of no return so its not a big deal for me. I find is VERY hard to believe that someone who purchases a mid-level DSLR has ZERO experience with cameras. That is unfathomable to me. Even if you have used a simple P&S then you know about what you should need a flash, if you've EVER used a basic film camera, then you should easily be able to tell about ISO. Nobody purchases this camera and have NO idea as to what they are doing, thats a recipe for crappy pictures and never liking DSLRs. With P mode on the D80 it selects the best combination of settings (aperture and shutter) for the given situation. If you don't like that, say you want soft water for instance, you can turn the dial on the back of the body and this symbol will appear (P*) and it shows you've changed the settings, but it still keeps the correct exposure. You can even leave "auto iso" on in P mode.
With auto mode, what you see is what you get. If the lighting conditions aren't the best, then you'll get subpar shots but the camera will try its hardest to give you all its got. But it still won't look quite right. Most shots with a dslr require some amount of effort. Whether it be changing your shutter, your aperture or your iso, we have these cameras because we enjoy having the control of doing what we want.
The point is, you are very limited to what you are going to get with the auto mode, whereas the P mode will give you a lot more options and often times, allow you to make a picture that looks better. The D80 is no slouch of a camera, nobody can deny that, so any subpar pictures it takes, is (and i'm sorry but I mean no offense) the picture takers fault for not knowing the correct settings. On Auto, you can't choose those settings, on P mode, you can at least edit the cameras 'guess' to get something more of what you are looking for.
Hopefully that makes sense.