Headers and footers are areas in the top, bottom, and side margins of each page in a Word 2007 document.
Why would you want to use them? You can use them to automatically add things like...
- page numbers
- the date
- the title or file name of your document
- your library's logo
- your name
- the URL of your library's website
You can read instructions on how to do each of the above at the Insert Headers and Footers page. Or if you prefer to see screenshots & screencasts with an audio description, choose instead the Header and Footer Basics tutorial; here's a sample from it: