Alice11 and bdemaria are giving you excellent answers, but perhaps you should do some more reading.

RinR maintains a phenomenal website, Ron in Rome, and his train articles might address some of your basic questions (however, the new Italo is not discussed):

Updated February 2011:
Buying Train Tickets – Updated

Updated March 2012:
Trenitalia and Booking Online, Using the Trenitalia Website – Updated

And the Slowtravel site maintains informational pages on train travel within Italy. Many of these articles are older, but for basic informational purposes they could be useful to you:
Trains in Italy

And in this ST thread there's currently one review of using Italo and some discussion comparing Italo with Trenitalia:
NTV (Italo): New Trenitalia competitor for high-speed rail

And I'm assuming you've already read this FTer thread which Alice11 linked above:
http://www.flyertalk.com/forum/italy...-operator.html