Places any number of objects into a "Tag". The tag can then be referred to in a game script.
To create a tag, select the object(s) that will be in the tag (hold left shift to select multiple objects). Then type the name of the tag in the text field and click "create".
To add objects to an existing tag, select the name of the tag from the list. All objects in that tag should now be selected. Hold left shift and select the additional object(s). Click "Apply". Unfortunately, there is no way to remove an Object from a tag (if you have an unwanted object in a tag, you'll need to delete the tag and re-create it).