Please Help, What is the benefits of E or I infront of keyword domain?
 

I saw people try to get a letter E or I infront of keyword domain. Example: Ebuy, Esupport, Ipoker, Itrip, ,,ect. 1. Can anyone explain me the benefit of this domain? and how how it will be worth if I own Elaw, or Ilaw, ect? 2. If we compare E & I which one will be the most in selling...