Slide show created by Microsoft PowerPoint, a program used to create personal and professional presentations and slide shows; includes a finished collection of slides; used for saving finalized presentations and for slide show playback.
PPSX file open in Microsoft PowerPoint 2016
Once saved, PPSX files cannot be edited and may only be viewed. Therefore, they are useful for sending finished presentations to users that do not own the commercial version of PowerPoint, since the PPSX file can be viewed with the free PowerPoint Viewer program.
PPSX files are saved in the Open XML format, which was introduced in Microsoft Office 2007. They may be opened by PowerPoint 2007 or later, or by earlier versions of PowerPoint with the Open XML component installed.
NOTE: Even though OpenOffice.org does not natively open PPSX files, you can still open them in the software by selecting the "Microsoft PowerPoint 2007 XML" option from the list of supported file formats.