As you learned in Chapter 21, a layout is a positioning template. The layout used for a slide determines what content placeholders will appear and how they will be arranged. For example, the default layout, called Title and Content, contains a placeholder for a title across the top of the slide and a multipurpose placeholder for body content in the center.
A theme is a group of design settings. It includes color settings, font choices, object effect settings, and in some cases also a background graphic. In Figure 22-1 later in the chapter, the theme applied is called Concourse, and it is responsible for the colored swoop in the corner, the color of that swoop, and the fonts used on the slide. A theme is applied to a slide master, which is a sample slide and not part of the regular presentation, existing only behind the scenes to provide its settings to the real slides. It holds the formatting that you want to be consistent among all the slides in the presentation (or at least a group of them, because a presentation can have multiple slide masters). Technically, you do not apply a theme to a slide; you apply a theme to a slide master, and then you apply a slide master to a slide. That’s because a slide master can actually contain some additional elements besides the formatting of the theme such as extra graphics, dates, footer text, and so on.