Displays how ratings will be effected if user1 played user2. If both parameters are omitted and you are playing a game, then the command will display the possible ratings changes from your game with your current opponent (if you are not playing a game, you will be told that). If only user1 is given, then the command will display the possible ratings changes from a game you would have with user1. If both parameters are given, then the command will display possible ratings results of a game between user1 and user2.
See also: match