If a questioner guesses the correct answer, they win and become the answerer for the next round. Sample questions could be: ' Is it bigger than a breadbox?', 'Is it alive?', and finally 'Is it this pen?' Lying is not allowed. In variants of the game, answers such as 'maybe' are allowed. They take turns asking a question which the answerer must answer with 'yes' or 'no'.

In the traditional game, the 'answerer' chooses something that the other players, the 'questioners', must guess. It escalated in popularity during the late 1940s, when it became the format for a successful weekly radio quiz program. It originated in the United States and was played widely in the 19th century. Twenty questions is a spoken parlor game which encourages deductive reasoning and creativity. For the computer-human game show, see 20Q (game show).