This dialog is displayed when selecting a path in the content tree, e.g. when setting the Path property of some menu web part.
When selecting a path, first choose the site whose content tree should be displayed using the Site drop-down list.
The content tree of the site gets displayed. By clicking a document in the content tree, all items stored under it are listed in the right part of the dialog. By clicking the Show sub-documents () button, the document's sub-documents will be displayed in the list.
You can select the document by clicking it either in the content tree or in the list. Path of the selected document gets filled in the Selected path field. Click Select to confirm your selection.