These are Document Properties!

They help standardise a document: eg:

You create a Cover Page using Quick Parts, and fill in the: Document Title, Document Subtitle, Date and Author (defaults to computer account name). Then, later in your document, you can add the Document Title Property and it will take the information form the Cover Page info that you filled in!
Alternatively you can go to Properties and fill in all the info before you start the document, then, when you add a Document Property Object, it will take the details straight from the properties!

To make one is simple:
In the Insert Tab, choose to insert a Text box, then go back to the Insert Tab (as it will change to the Text Box Tools, Format Tab) and click on Quick Parts > Document Property and add the property of your choice!

TTFN!