This must be a pre-existing, legal VRML node reference. This node could be anything, including a node previously created with a createVrmlFromString call, that has not been added to the scene yet. You can use anything, so long as it is not null. The third argument is a string. If you had a Grouping node you could pick either the addChildren, removeChildren or children fields of the node as an example.
Lets look back at the example.
As you can see, there is a bit less code to do it this way. An alternative is that we can send the information back to the script itself for later addition to the scene. We might want to do some other processing of it for example. To use the script instead of the node directly, some extra changes are needed. This is the group that you will be adding the box to.