Given that Microsoft already has a presentation program in the form of the ubiquitous PowerPoint, the obvious question is: where does this fit in? The answer is that it is less formal and more free-flowing. In PowerPoint, the emphasis is very much on creating material - you painstakingly handcraft slides with text and illustrations. In Sway, you incorporate material from online sources, such as Facebook, Bing, YouTube and OneDrive. To help you, Sway is intelligent enough to suggest appropriate content, based on what you are doing and what you have done before. Another way of assessing it is this: if you were putting together a comprehensive presentation for a large meeting of people you might use PowerPoint. But if you had to quickly put something together for a couple of people you might use Sway on an iPad and hand it round the gathering.
Pitched as a 'next generation' presentation tool, will Sway replace PowerPoint? Probably not. But it would not be surprising if some of the ideas make their way into future versions of PowerPoint, albeit not PowerPoint 2016 which is already largely done and dusted.