Minecraft wiki entry for JSON_format, associated text:  conditions:
 player: The player that would get the advancement. May also be a list of predicates that must pass in order for the trigger to activate.
All possible conditions for entities[show]
 start_position: A location predicate for the last position before the player teleported to the Nether.
Tags common to all locations[show]
 distance: A predicate for the distance between the position of the player when they entered the Nether and when they exited it.
 absolute:
 max: The maximum value.
 min: The minimum value.
 horizontal:
 max: The maximum value.
 min: The minimum value.
 x:
 max: The maximum value.
 min: The minimum value.
 y:
 max: The maximum value.
 min: The minimum value.
 z:
 max: The maximum value.
 min: The minimum value.