what is the meaning of elo in chess?

Answer 1

Elo Rating : A mathematical system, now used worldwide, devised by Prof. Arpad Elo to rank chess players according to their performances.

Answer 2

The Elo rating system was developed by the US Chess Federation to allow players to match up to players of comparable skills by assign points that are adjusted for each rated game. It is now the basis for most of the ratings systems used in non-chess game sites as well, including Yahoo Games, Mystic Island, MSN, etc.