InterRail is a train pass that allows unlimited travel by train for up to one month throughout many European countries. It was created in 1972 to celebrate the 50th anniversary of the International Railway Union. Originally intended for those under 21, the age limit was later extended. Over time, more countries participated as InterRail expanded after the fall of the Iron Curtain. Today there are different ticket types depending on age and duration. InterRail aims to give young people an affordable way to explore Europe by train.