Slide Master view is a very important view within PowerPoint — if you make any changes or edit within this view, these modifications will influence all slides within your presentation. For example, if you want to make your company logo appear on all the slides, you will have to add the logo within the Slide Master — or if you want the font size of your slide titles to be a little larger or smaller, then those edits also need to be made in the Slide Master.
Learn about the Slide Master view in PowerPoint 2013 for Windows.

