What is an "Elo rating"?

An "Elo rating" is a calculation used to determine a player's relative skill level based on their performance in competitive play. This rating system works by adjusting a player's score based on the outcome of matches against other players, taking into account both players' ratings. When players compete, their scores are updated, reflecting their win-loss records relative to the strength of their opponents.

In competitive environments like Magic: The Gathering tournaments, Elo ratings can help to create more balanced pairings in Swiss rounds, ensuring that players face opponents of similar skill levels over the course of the event. The system is effective in identifying a player's progress and skill relative to others in the same competitive scene.

The other options do not correctly define what an Elo rating is; while it can aid in player pairing and is influenced by match outcomes, its primary purpose is to calculate and represent a player's skill level in a relative manner.