Stockfish is a free UCI chess engine derived from Glaurung 2.1.  It is not
a complete chess program and requires some UCI-compatible GUI (e.g. XBoard
with PolyGlot, eboard, Arena, Sigma Chess, Shredder, Chess Partner, or
Fritz) in order to be used comfortably.

Read the documentation for your GUI of choice for information about how to
use Stockfish with it.

WWW: http://www.stockfishchess.com/