Arpad Elo was a Hungarian-American physics professor and chess player, best known for developing the Elo rating system. Born on August 25, 1903, he created this system to calculate the relative skill levels of players in two-player games, particularly in chess. The Elo rating system uses a mathematical formula to update player ratings based on game results, allowing for a dynamic assessment of skill. This system has been widely adopted in various competitive games and sports, making it a standard for ranking players globally. Elo passed away on November 5, 1992, but his legacy continues in competitive gaming.