A train ticket is a voucher issue by a railway operator that enables the bearer to travel on the operator's network. Tickets can authorize the bearer to travel a set itinerary at a specific time (common for long-distance railroads), a set itinerary at any time (common for commuter railroads), a set itinerary at multiple times, or an arbitrary itinerary at specific times. (The last two categories are often called passes: the former is often sold as a discounted block of trips for commuters; the latter is often sold to vacationers -- for instance, European Eurail passes.)