The master defines title and bullet styles, background, color scheme, animations, and common identifying information, such as slide numbers, dates, and footers.
Any element or formatting on the slide master can be overridden on individual slides or objects.
PowerPoint presentations work with a pair of masters, now called a slide-title master pair. One of the masters, the title master, determines the formatting for slides that have the Title Slide layout applied. The other master, the slide master, determines the formatting for slides that have all other layouts.