Styles give your document a consistent, professional look.
Select the text you want to format.
Tip: If you place your cursor in a paragraph, the style is applied to the whole paragraph. If you select specific text, only the selected text is formatted.
On the Home tab, point to a style to preview it.
If you don't see a style you want, click the More button to expand the gallery.
Select a style.
Using Headings allows you to move parts of the document around by using View > Navigation Pane and then moving the listed headings up or down in the doc. Headings also can be used in creation of a table of contents.
Note: If you need a different look, go to Design > Themes and select a new one. Each Theme has its own set of Styles.
Use the Navigation pane in Word
Customize or create new styles in Word