PowerPoints and Google Slides are two systems for creating presentations and slideshows. PowerPoint is an Adobe product commonly used in Windows. Google Slides comes automatic with every Google or Gmail account, and operates similar to Google Docs. Here's a list of the differences between them, provided by Educba.
There are many websites and videos online that can help you make presentations in either of these formats. Some are included below, but feel free to search on your own and find one that works for you. Just keep in mind that both PowerPoint and Google Slides update periodically, and you should be using a set of directions that applies to the version of the program you're using.