Unlike slides which are primarily presented through a display device such as a monitor, TV screen or projector, the Notes and Handout pages in PowerPoint are essentially intended for printing. The terms Header and Footer typically come from word processing programs. They denote repeated elements that show at the top and bottom of every page. Headers and Footers work similarly on PowerPoint Notes and Handout pages.
To learn more, choose your version of PowerPoint. If we do not have a tutorial for your version of PowerPoint, explore the version closest to the one you use.