Italian Regionale (or Regional) trains, operated by TrenItalia are the most basic train services available in the country. They operate within a single area, stopping at most stations on a route. These local services are generally much slower than Inter-City alternatives, and tend to be a little scruffy, a bit older, but most importantly, cheap.
TrenItalia operates a fleet of around 800 trains, with nearly 5,000 carriages, with thousands of services running each day.
Regionale train tickets can now be booked in advance online, and can also be printed at home. You will need to register on the TrenItalia website to take advantage of this facility.