Some of the terms in the Domain Performance report can be difficult to interpret.  Here is an overview of the meanings:

Visits, New Visits, Pageviews, Unique Pageviews - These are all pulled from Google Analytics, which is enabled on all domains.  The official definitions are here: http://www.google.com/support/analytics/bin/answer.py?answer=57164

Item Clicks - These are clicks on products which led to the store that sells the item.  This does not include internal clicks to our own on-domain product pages. 

RST, LST, RSM - These are individual ad units on a domain, which are short for "Right Side Tower", "Left Side Tower", and "Right Side Middle."  Impressions will appear for these ad units if an ad is placed in them.  Revenue will appear for them only if the ad is configured as an adsense unit in Google Ad Manager (the content team can implement this for you).