A fare is the fee paid by a passenger for use of a public transport system: rail, bus, taxi, etc. In the case of air transport, the term airfare is often used. Fare structure is the system set up to determine how much is to be paid by various passengers using a transit vehicle at any given time. A linked trip is a trip from the origin to the destination on the transit system. Even if a passenger must make several transfers during a journey, the trip is counted as one linked trip on the system.

Public transport is a system of transport for passengers by group travel systems available for use by the general public unlike private transport, typically managed on a schedule, operated on established routes, and that may charge a posted fee for each trip. There is no rigid definition of which kinds of transport are included, and air travel is often not thought of when discussing public transport—dictionaries use wording like "buses, trains, etc." Examples of public transport include city buses, trolleybuses, trams and passenger trains, rapid transit and ferries. Public transport between cities is dominated by airlines, coaches, and intercity rail. High-speed rail networks are being developed in many parts of the world.