A "Rail Pass" is a travel document that allows unlimited travel on a specific rail network for a set period. It is popular among tourists and travelers who want to explore multiple destinations without purchasing individual tickets for each journey. Rail passes can vary in duration and coverage, often including various train services and routes. Many countries offer their own versions of rail passes, such as the Eurail Pass in Europe or the Japan Rail Pass in Japan. These passes can provide significant savings and convenience, making them an attractive option for those planning extensive train travel.