Word's built-in Styles
Many features in Word (such as fields, headers and footers, AutoText, numbering) automatically apply their own built-in style. Whether or not you choose to manually use styles, these built-in styles are present in your document and Word users need to understand how they work in order to edit and format documents on a consistent basis. Each new version of Word adds more pre-defined styles (such as the new numbered list styles in Word 2002).
One problem you run into with lists is the List Number button on the Formatting toolbar. In previous versions of Word, it always applied a predefined list numbering format. In Word 2000, this was changed and applies an Outline List Template style, and the List Template it applies is the one most-recently used in the document. The numbering button isn't consistent and can cause unexpected results because it can change the underlying "style" that is built in.
If you select a paragraph and choose Format/Bullets and Numbering and choose one of the List Templates, this will make the List Template you chose the new default. From then on, each time you click that button, it will apply exactly the same List Template. If you share that document with someone else, the numbering applied by that button changes to the default List Template on that machine. If another person on a different machine opens the document, the numbering they apply will be different again. Yet all three times the users hit exactly the same button whenever they wanted numbering. If you create a custom list style (that is not linked to another style), the numbering remains stable from user to user and machine to machine. Your styles stay with your document, even if you send the document to someone else who uses different styles -- the recipient needs to make sure Automatically update document styles is not checked in Tools/Templates and Add-ins.
Using styles alleviates the need to remember hundreds of macros and will automatically format documents on a consistent basis. Consistency also makes editing easier when it comes to making global changes. If you decide that all of your section headings should be underlined and centered (instead of left-aligned and bolded), you modify the style definition and you’ve changed every heading in your document in one fell swoop.
So many Word users break out in a cold sweat when they read about styles. They're convinced that styles are complicated. Nothing could be further from the truth! You can modify any of the built-in styles or simply type and format a line or paragraph the way you want it, position your cursor anywhere in the new text, go to Formatting/Styles, click New and type a name for the new style (click on New Style in Word 2002 task pane), assign a keyboard shortcut key if you want, check the box to add the style to your template, and press Enter. Your new style is ready to use. Rather than having to apply each attribute to several blocks of text, you can do it all at once by simply modifying the style.
Styles are designed to be very powerful and can help you **dramatically** improve your productivity. They save you enormous amounts of time if you find yourself applying the same formatting over and over again, or if there's the slightest chance you'll want to change formatting of similar data scattered throughout a long document.
Just another viewpoint. :)