I already talked about the subject of elo rating but decided to expend previous article with more information and some technical details about elo chess rating system. This article is not recommended for people who take statistics/predictions way too seriously since this information can ruin their chess results. So read it at your own risk!
The ELO chess rating system is a method of estimating the strength of two players. ELO system isn’t an IQ score. ELO rating does not show how smart you are, how well your memory is, how fast can you calculate chess variations or recognize chess patterns (it is a topic of a separate discussion, how well the IQ score reflects all of the above).