You probably have seen this one in different documents and even books. Once you check this option, the stuff you put in the header of the first page won't appear on other pages and conversely, if you change the header of any other page it won't affect the first page. In the Header & Footer Tools tab, in the Options section, check Different First Page. So far, anything that you add to the header will appear on every other page but what if you don't want the header on your first page to appear on every page in the document? You might want to have other content in the header of other pages or anything else. This tab allows you to change options related to the header and also insert components other than plain text to it. The Header & Footer Tools tab activates whenever you're editing the header or the footer of a page.
