D800 ADL

I am trying to learn about how active D lighting actually works in D800. I did some google searching and i found may tutorials on how to turn it on/off but i did not find answers to the following questions:

1. How does D-lighting actually effect the image? Does it force location varying ISO to bring up the shadows and bring down the highlights?

2. Is ADL effect only applied to JPG or does it effect exposure of the raw file?

3. What is the EV equivalent of different ADL levels?

4. Does ADL only effect deep shadows and blown out highlights? I took a set of pictures cycling through ADL levels and they all look the same, but i only had mid-tones in the frame... i guess ADL ignores mid tones?

5. Is there a reason to not have ADL on auto and just forget it even exists? How can ADL screw me?

I shoot RAW+jpg.

Thanks ahead.