If you are in the middle of a PowerPoint slideshow, you can easily pause the show while it is on screen. When you do, the screen will turn black, giving you the opportunity to have the undivided attention of your audience. To accomplish this, press B while in your slideshow. To return to the presentation, simply press any key.
Alternatively, if you prefer the screen to turn white, press the W key instead. Again, press any key to return to your slideshow.