When you edit the Slide Master, all the existing and new slides that follow that slide master will change automatically. What Is A Slide Master?Ī Slide Master or a Master Template is a set of defaults. If you make the same changes to that template or all templates that you use then why not simply edit once? Editing once in the Slide Master will apply those changes to the whole presentation. Editing a slide master is a smart way of making changes to a presentation template.