Although it's easy to add a new slide to a presentation, choosing the right slide layout isn't always so simple.
PowerPoint supports two broad categories of slides: title slides (typically the first slide in a presentation), and "regular" slides (which, confusingly, are usually just called "slides"). PowerPoint has one predefined layout for title slides, and almost two dozen predefined layouts for regular slides.
Slide layouts aren't static: You can change a slide's layout by selecting the slide, choosing Format, Slide Layout, and applying a layout (by clicking it) from the Slide Layout pane
Whether you're applying a layout to a brand-new slide, or changing the layout of an existing slide, ...