Where do I find an explanation for the different train fares in Italy?

I would like to see a better explanation myself; I never could figure out the rail pass thing with all the lingo. I ended up buying our tickets after we got there, doing the "point to point" method on the day, or day before, we actually needed them. You can skip train station lines by using the self service kiosks in the many train stations; there are English options. Buying point to point is easy enough; I'd recommend, if you can, to look up the train schedule online and find out what time you want to leave, and on what train. Take that train number to the train station and give it to the ticket window person. (trains marked with "R" are regional trains. they are cheaper, but stop at a lot of stops. The "ES" trains are the faster trains that don't stop a lot, and of course are more expensive. I equate the regional trains to city buses and the ES trains to Greyhound buses as far as how many stops they make). Good luck!

The fastest and most expensive trains in Italy are the:

AV, ES-Fast and ES

Other fast trains (less expensive than those above):

ES-City and IC

Inexpensivfe local trains for commuters (no seat reservation possible)

R = Regionale

Night trains:

ICN, EXP

International trains:

EC

International night trains:

ECN

Try the following link:
http://www.trenitalia.com/cms/v/index.jsp?vgnextoid=227f805cc9740210VgnVCM1000003f16f90aRCRD