This setting, if enabled, will make the nozzle move up slightly with a Z hop during the switching of extruders.
Switching extruders brings in a nozzle that has had some extra time to ooze, so you may decide to give this a bit of a higher Z hop than the normal Z hops during the print.
If a prime tower is printed, this will only increase the Z hop height when travelling away from the print and to the prime tower. Since blobs on the prime tower are sort of expected anyway, it's not effective to increase this setting too much when using a prime tower.