The Italy train system and rail network is very well-developed with over 25 thousand kilometers (about 17 thousand miles) of rail tracks, meaning you can take trains across Italy and reach practically any destination on the country's continental part that you need.
Trenitalia is the major Italy trains company which is responsible for operating both regular and high-speed trains. The high-speed Italian rail network connects cities like Rome, Florence, Naples, Bologna, Milan, and Venice (among many others) by modern Italy bullet trains.
Italo Train (aka "Italo Treno") and Frecciarossa are among the best brands.