When I first read your question, I thought you might be referencing mobile-checkin, which is starting to become popular. As I looked into your question, I think this is just fancy wording for the ability to show your email at a checkin counter, where they will pull up your info and print your boarding pass.
Taken from wikipedia electronic ticket:
To check in for a flight with an e-ticket, the passenger usually goes
to the check-in counter in the usual manner. There they may be
required to present some personal identification, a credit card or the
e-ticket itinerary receipt. Theoretically it is not even necessary to
present the e-ticket itinerary receipt document or quote the
confirmation code or e-ticket number as the reservation is confirmed
solely on the basis of the passenger's identity, which may be proven
by a passport or the matching credit card. However, producing a
print-out of the itinerary receipt is required to enter the terminal
of some airports as well as to satisfy immigration regulations in most
At the check-in counter, the passenger checks-in his/her luggage and
receives a boarding pass. However, electronic ticketing allows various
enhancements to checking-in.
If your ticket does give you a barcode with a seat number (like below), then you can use this as your actual boarding pass. TSA and the gate attendants just ask to place your mobile device on their scanner. I typically use this for domestic flights in the states, but I haven't seen this for international flights from the US.