Word 2013 includes a new feature that lets you collapse and expand sections of your document. If you are working on a long document, you can focus on a specific section by collapsing all the sections except the one on which you are working. You can also use this feature to entire sections within a document.
Expanding or Collapsing a Section of a Document
In order to expand or collapse a document section, you must use Word’s built-in heading styles. After applying a heading style, a small gray triangle will appear to the left of the text.
Simply click the triangle to collapse the document section. Click the triangle again to expand that part of the document.