"Recycling bin" is the parent node for the nodes that are no longer used on the main tree. Since these nodes are not deleted, if needed, they can be "recycled," i.e. their content can be reused or they can even be restored on the main tree in some form.
To send a node to Recycling bin:
- assign "Recycling bin" as a new parent.
- disconnect it from its other parents.
- reconnect its children to other -- undeleted -- nodes.
- reassign internal links pointing to the deleted node to other, undeleted nodes.