A ticket is a voucher that indicates that one has paid for admission to an event or establishment such as a theatre, movie theater, amusement park, zoo, museum, stadium, concert, or other attraction, or permission to travel on a vehicle such as an airliner, train, bus, or boat, typically because one has paid the fare. Also a ticket may be free, and serve as a proof of reservation.
One can buy a ticket at a ticket window or counter, called a box office in the entertainment industry (this term is also used for the total receipts). The ticket check may also be there, or it may be separate. Tickets are also available from resellers. Resellers typically are commercial enterprises that purchase tickets in bulk, and resell them to members of the public, adding a surcharge. Consumers patronize resellers for reasons of convenience and availability. The convenience factor relates to being able to obtain tickets locally, and also being able to make alternate selections on the spot if the preferred performance is not available. The availability factor relates to the fact that all tickets may have been sold out at the box office, requiring the purchaser to either obtain tickets from the reseller, or not to see the show (or at least not see the particular performance of choice).
A ticket may be valid for any seat ("free seating") or for a specific one ("allocated seating"). Sometimes, ex: for some train journeys, both are available, with an increased charge for a reserved seat. Free seating in a train means the risk that one has to stand, but in ex: a cinema it means a seat is guaranteed, just not a specific one.
Paper or card is generally used, although plastic may be used instead for durability. Some have a barcode or magnetic stripe for keeping simple data stored on them, higher end ones use chips to store more data and prevent counterfeiting.
A paper ticket often is perforated so it can be separated into two parts, one (the ticket stub) to be kept by the customer, and one to be kept by the ticket controller. Whether or not one can leave and reenter with the customer part only varies. It may not be allowed to avoid subsequent use of one ticket by multiple people, or even simultaneous use by giving the ticket to someone before the ticket check (if this is physically possible), but it may also be allowed, ex: in a movie theatre to buy, during a movie, a snack or drink before the ticket check and reenter.
Tickets may be printed in advance, or fully or partly printed when issued, or it may be a printed form that is completed in handwriting (ex: by a train conductor who does not carry a ticket machine, but just a supply of forms and a pen).