The largest train operator in Italy is Trenitalia, which is a division of the Italian government. The company has been in existence since 1905, and the train network throughout Italy has been steadily growing and improving – it's by far the easiest and most cost-effective way to get around the country.
The fastest trains operated by Trenitalia are the Alta Velocità (AV) series, called – in descending order of speed – the Frecciarossa (“Red Arrow”), Frecciargente (“Silver Arrow”), and Frecciabianca (“White Arrow”). These only connect a short list of Italian cities, however – Turin, Milan, Bologna, Florence, Rome, Naples, and Salerno. The Frecciarossa trains can reach speeds of up to 190 MPH (300 km/h). Reservations are required on AV trains.
InterCity trains are the next-fastest option, running at up to 125 MPH (200 km/h), and connecting mid-sized cities and towns across long distances as well as the biggest cities served by the AV trains. Reservations are also required on InterCity trains.
The slowest Trenitalia trains fall under the category of “regional” trains, and go by names like “Regionale,” “Diretto,” and “Espresso.” These are intended to serve every last small town with a train station, and they typically stop at every single station between two larger cities. If you're in a hurry, this isn't the best news – but if you're headed to a more remote part of Italy, this may be your only option.