The plugin will add a button to the visual editor to run the iTunes Link Generator and offers link masking to hide your affiliate junk.
Ok it's not an easy question, i know what goes in them for me and some others, but some of yours are going to be different otherwise you're going to be using someone elses affiliate details. But heres the short version to your answer..
Affiliate ID - this is your iTunes/PHP Affiliate ID, you will see it in the top right hand corner when you login to the PHG affiliate area.
Questions anyone? feature ideas? i've got some thoughts on where i'd like to take it, but your input is appreciated.