From Word Help:
{ [REF] Bookmark [Switches ] }
Inserts the text or graphics represented by the specified bookmark
(bookmark: A location or selection of text in a file that you name for
reference purposes. Bookmarks identify a location within your file that you
can later refer or link to.). The bookmark must be defined in the active
document (active document: The document in which you're working. Text you
type or graphics you insert in Microsoft Word appear in the active document.
The title bar of the active document is highlighted.). To insert bookmarked
text or graphics from another document, use the INCLUDEPICTURE or INCLUDETEXT
field. The Cross-reference command (Insert menu, Reference command) inserts
REF fields to create cross-references.
In most cases, you can use the bookmark name instead of the REF field. Using
the REF field is optional except in cases where a bookmark name matches a
Microsoft Word field name. For example, if the bookmark name is "Title",
which matches the Word field name TITLE, you must use the REF field instead
of the bookmark name. The field { REF Title } inserts the text represented by
the "Title" bookmark, whereas the field { Title } inserts the contents of the
Title box on the Summary tab in the Properties dialog box (File menu).
Note When you insert text copied from another location in the same
document, the Paste Special command (Edit menu) inserts a REF field with the
bookmark INTER_LINKn, where n is incremented automatically. You should not
edit an INTER_LINKn bookmark in a REF field. Also note that REF fields with
INTER_LINKn bookmarks in a mail merge main document can cause errors during
merging.
What I do is go to Insert\Field and choose the Ref option.