If you edit the slide master or layout masters after you create individual slides, you’ll need to reapply the changed layouts to the existing slides in your presentation in Normal view. That way, all the slides that you add to your presentation are based on your custom edits. Note: It's a good idea to edit your slide master and layout masters before you start to create individual slides. To edit that thing, you must switch to Slide Master view.

Conversely, if you're working in Normal view and find that you're unable to edit an element on a slide (such as, 'why can't I remove this picture?') it may be because the thing you're trying to change is defined on the slide master or a layout master. When you make changes to layout masters and the slide master in Slide Master view, other people working in your presentation (in Normal view) can’t accidentally delete or edit what you’ve done. However, the majority of changes that you make will most likely be to the layout masters related to the master. When you edit the slide master, all slides that are based on that master will contain those changes. The related layout masters appear just below the slide master (as in this picture from PowerPoint for macOS): The master slide is the top slide in the thumbnail pane on the left side of the window. To open Slide Master view, on the View tab, select Slide Master: When you want all your slides to contain the same fonts and images (such as logos), you can make those changes in one place-the Slide Master, and they'll be applied to all your slides.

Slide master powerpoint definition