Notes in simfiles can be hit with various accuracy which results with various judgements. Judges (j4, j5, etc.) determine what timing is required for certain judgments to be shown on the screen. The default timing windows set is j4. Changing judge also changes the curve of dance points given to the player (e.g. a higher judge gives lower score for the same level of accuracy as on a lower judge).
The amount of dance points given for hitting with certain accuracy used to depend solely on timing windows and the values assigned to judgements in the MAX DP system. In Etterna, Wife Dance Points are used instead, with a curved function replacing the old assignments of points to judgements.