The purpose of the slide master in PowerPoint 2010 is to allow users to make universal style changes to all the slides in their presentation. It is a special mode in PowerPoint that allows users to modify slides and slide layouts in their presentation. By editing the slide master, users can affect every slide in the presentation, and by modifying individual slide layouts, they can change any slides using these layouts. The slide master controls the overall appearance, such as formatting and design, of each slide layout, and therefore each slide in the presentation. Some common uses of the slide master include changing the font, inserting a footer across all slides, and setting the background and color scheme for the presentation. Using the slide master is a simpler and more graceful way of applying changes to the entire slide, rather than using copy/paste and format painting to make changes to different sections within the presentation.