The terms Header and Footer typically come from word processing programs; these denote repeated elements that show at the top and bottom of every page. Headers and Footers work similarly on PowerPoint slides: the Footer is a line of text that usually appears at the bottom of a slide. Typically, the Footer area includes three placeholders: Date, Footer, and Slide number. By default, the footer with one or more of these three placeholders appears on every slide in a presentation, but you can change that as required.
Learn how to add Headers and Footers to slides in PowerPoint 2016 for Windows.