Instead of having a straightforward switchover from one slide to the next, you can set PowerPoint to play a transition—an effect that smoothes, animates, or dramatizes the change of slides.
You can set a different transition for each side if necessary. You specify the transition by selecting the slide and choosing the transition to play when the slide appears (as opposed to setting the transition for when PowerPoint changes the slide to the next).
NOTE: Depending on the presentation template or design you're using, some or all of the slides in the presentation may already have transitions applied to them. If so, you can leave them as they are, customize them, or replace them with other transitions.