A family of Microsoft presentation graphics products that offer tools for creating presentations and adding graphic effects like multimedia objects and special effects with text.
You can incorporate the stock images and videos included with Office in PowerPoint presentations you create without concerns about copyright. You may NOT distribute the images/videos *as* images/videos, though.
Another possible concern: depending on your Office license, you may not be permitted to use it for commercial work. I'd imagine that means that a YouTube channel that you create for your own entertainment, to share with friends or perhaps even for a non-profit agency would be ok, but if you intend to monetize your work, it might be best to license one of the versions of Office that permits commercial work.