The header and footer workspace.
Before we go into specifics, here's a word about the header and footer workspace. This workspace includes areas at the top and bottom of a document page that are specifically for header and footer content. After you've inserted a header or footer, the areas become active and editable, and they're marked with a dashed line, as the picture shows.
The main point is that header and footer content inhabits a layer of the document that is separate from the main body. This is because headers and footers behave differently than your document's main content. When you add one header or footer, such as a page number or date, it appears on every page. In the case of page numbers, they're also programmed to be consecutive and to update themselves automatically when the number of pages changes.
As you apply and work with headers and footers, you'll get used to the header and footer workspace and see how to open and close it.