ELO is a rating system is a method for calculating the relative skill levels of players in two-player games such as chess and Go. ELO is not an acronym. It is the family name of the system's creator, Arpad Elo (1903–1992), a Hungarian-born American physics professor.
ELO was originally invented as an improved chess rating system although it is used in many games today. It is also used as a rating system for competitive multi-player play in a number of computer games. For more information on ELO go to wikipedia.org