A timetable is a list or chart of the exact times buses, trains, or other modes of transportation are scheduled to arrive and depart. If you travel around Europe, you'll need a train timetable.
In the U.K., a class schedule is sometimes called a timetable, while in North America it usually refers to a transportation schedule. You can find most timetables online, or you can carry one with you when you're in an unfamiliar city. Timetables tend to change over time, as new routes are added or exact departure times are adjusted.