This command can be used to reset the XP Data of a single user, for example to punish them for breaking rules, or for the entire server.
You will receive a warning when executing the command, asking you if you are really sure you want to reset the XP Data.
By not entering a username, user ID or user mention you will attempt to reset the server XP. This resets the XP Data for all users on the server, even if they have left the server between them gaining XP and you resetting the XP.