A paper ticket is generally only good on the airline for which it was purchased. However, an airline can endorse the ticket so that it may be accepted by other airlines, sometimes on standby basis or with a confirmed seat.
Usually the paper ticket is for a specific flight. It is also possible to purchase an 'open' ticket which allows travel on any flight between the destinations listed on the ticket. The cost for doing this is greater than a ticket for a specific flight.
Some tickets are refundable. However the lower cost tickets are usually not refundable and may carry many additional restrictions.
A ticket is made up of one or more flight coupons. These flight coupons are the actual tickets that are used for travel. One flight coupon is used for each leg of the flight.
The carrier is represented by a standardized 2-letter code. In the example above Thai Airways is TG. The departure and destination cities are represented by International Air Transport Association airport codes. In the example above, Munich is MUC and Bangkok is BKK. The International Air Transport Association is the standard setting organization.
Only one person can use a ticket. If multiple people are traveling together, the tickets are linked together by the same record locator or reservation number which are assigned if the tickets were purchased at the same time. If not, most airlines can connect the tickets together in their reservation system. This allows all members in a party to be processed in a group allowing seat assignments to be together (if available at the time of the assignment).
Standby tickets are obtained at the airport itself, only hours before departure. They represent places freed up by people who cancelled their flight shortly before departure (so the airline has free places available, yet can no longer sell it at at regular price because of the shortage of time).
Discount tickets are tickets that are only available at travel agencies; they are usually targeted at students. Discount tickets may be 50-70% cheaper than other similar regular tickets (not low-cost).