How do trains work in Italy?

Two systems that behave completely differently. High-speed trains — Trenitalia's Frecce and the private Italo — connect the big cities at 190mph, are booked for a specific departure like a flight, and get cheaper the earlier you buy. Regional trains (Regionale) serve everywhere else, cost a fixed low fare that never changes, aren't reserved, and let you take any train on that route within a time window. Rome to Florence is 1h35 on a Freccia; Florence to Siena is a regional. Stations are central, so city to city is genuinely door to door faster than flying.