Chess rating system
A chess rating system is a system used in chess to estimate the strength of a player, based on his performance against other players. They are used by all national chess organisations, and by FIDE, the International Chess Federation. In these systems a higher number indicates a stronger player. In general, a player's rating goes up if he performs better than expected and down if he performs worse than expected. The Elo rating system is used by FIDE and by many countries.