Got a long brief or other document that has lots of headings, subheadings, etc.? You need Styles, baby.
No, not style — Styles.
The Styles function in Word is a handy tool for, among other things, setting up headings for different sections of a document. These styles serve a dual purpose: not only do they help keep document formatting consistent (i.e., all paragraph and subparagraph headings at a particular level, for example, will be consistent through the document), they can help later when you create a Table of Contents, since Word can use these styles to create the levels of your Table of Contents.
There are a couple of different ways to use Styles & Formatting (as the feature is formally known) in your document.