Rock, Paper, Scissors, also known in Japan as Janken, is a hand game most often played by children. It was designed in Japan at the end of the nineteenth century and it was transmitted from Japan all over the world in the twentieth century. It is often used as a selection method in a similar way to coin flipping, Odd or Even, throwing dice or drawing straws to randomly select a person for some purpose, though unlike truly random selections it can be played with skill if the game extends over many sessions, because one can often recognize and exploit the non-random behavior of an opponent.
Various sports may use Rock, Paper, Scissors to determine which team gets the opening play (rather than a coin toss). Similarly, uncertain calls, or even the whole game in case of rain, may be decided by the game. It is also often used as a method for creating appropriately non-biased random results in live action role-playing games, as it requires no equipment.
The players count together to 3 counts, most commonly either using the name of the game (e.g. Rock! Paper! Scissors! or Ro! Sham! Bo!) or simply numbers. At the end of the third count, the players simultaneously change their fists into any of three "objects", which they then "throw" by extending it towards their opponent:
The objective is to defeat the opponent by selecting a weapon which defeats their choice under the following rules:
If both players choose the same weapon, the game is a tie and is played again.
In International competition, the weapon is thrown on the fourth count ("1 ... 2 ... 3 ... THROW"). This is called "International Style." In "American Style," the throw comes on the third count ("1 ... 2 ... THROW").
Typically, the game is played in a "best 2 out of 3" match.
Starting in 2002, the World Rock Paper Scissors Society (WRPS) standardized a set of rules for international play and has overseen annual International World Championships. These open, competitive championships have been widely attended by players from around the world and have attracted widespread international media attention. WRPS events are noted for their large cash prizes, elaborate staging, and colourful competitors. In 2004, the championships were broadcast on the U.S. television network Fox Sports Net.
Professional poker player Phil Gordon conducted what he called "The World Series of Rock-Paper-Scissors" during the 2005 World Series of Poker in which 64 contestents of the WSOP competed in a tournament similar to the NCAA tournament.
(Content courtesy of Wikipedia.)