The XOR label groups look the same as OR label groups, the only difference is that only one label of the group can be selected at any time.
See OR Labels for a configuration options for each label.
For the label group there are two additional options, compared to simple OR label groups
The select default label for new items can be used to choose one of the labels of the group which should be set when creating new items.
The ask for label when creating new items allows the user to select (another) label when creating new items.
Note: one small difference compared to Review labels: when selecting an XOR label of an item, the item is NOT automatically saved.