Contestant

A contestant is someone who takes part in a competition, usually a professional competition or a game show on television. The participants competing against each other have to go through rounds. The winners may have to compete in later stages or rounds until there is just one winner.
Game show contestants.
Game show contestants are usually members of the general public who are selected via some sort of qualification system, such as a general knowledge or IQ test (an example of this is "Jeopardy!", in which contestants must pass a 50-question test) who then appear on the televised show. Game show careers are usually short-lived, perhaps lasting only one day. A very small minority go on to achieve national fame, such as Joyce Brothers and Ken Jennings in the United States and Charles Ingram in the United Kingdom.
Some game shows deliberately target celebrity contestants, such as "Match Game" and "Blankety Blank".
There are links between game show contestants and other games and hobbies, such as Scrabble players who take part in word-based game shows like "Countdown" and "BrainTeaser".
Reality TV contestants.
Reality TV contestants are also selected from the general public, but again celebrity versions do exist. Shows like "Big Brother" select contestants from the general public by examining video logs that the contestants send in to the show. A small number, perhaps 10 or 15, are selected to live in a confined house separated from the outside world.
In general, reality TV contestants are set some task to do or achieve in a selected place, such as an isolated house or desert island, and are filmed for long periods of the day. In the case of "Big Brother", they are filmed up to 24 hours a day.