Fischer Random, also called Chess960, Fischerandom, FR Chess and FRC, is a chess variant, invented by Bobby Fischer, in 1996. At present, Fischer Random is the most popular chess variant and there are even Grandmaster tournaments. The popularity is due, in part, to the game employing the same board, pieces and piece-movements as traditional chess.
The critical difference is, the starting position of the pieces along the players' back rank is randomized. The random element renders the opportunity of obtaining an advantage through the memorization of opening moves unachievable, compelling players to rely instead on their talent and creativity. Fischer Random, which was based upon Shuffle Chess, retains full castling rights – resulting in 960 unique positions - hence, its common name - chess960.
One example randomised starting position in Fischer Random chess, chess960.
There are 959 random starting positions, plus the standard Chess set-up.
Before each game, a random starting position is determined and set up, subject to certain requirements (see picture, above). To maintain the integrity of standard chess, a player's bishops must start on opposite-colour squares, and the king must start on a square between the rooks. After setting up the board, the game is played in the same way as standard chess. In particular, pieces and pawns have their normal moves, including en-passant, promotion, etc., and the objective – checkmate – also remains the same.
Of note, Black's pieces are placed equal-and-opposite to White's pieces, as a mirror image. For example, if the white king is randomly determined to start on f1, then the black king would be placed on f8. The king never starts on the a- or h-files, since one rook must be either side of the king. The starting position can be generated before the game by computer program, or chosen by the players by a variety of methods using dice, coin, cards, etc. The nomenclature is more-or-less the same, although castling a-file / a-side (h-file / h-side), is used instead of castling-short / castling kingside (long, queenside).