Does a PPS (PowerPoint Show) need PowerPoint or a Viewer to play? Can I edit a PPS?
Yes, you need either PowerPoint or the PowerPoint viewer to play back PPS files.
The difference between PPS (PowerPoint Show) and PPT (PowerPoint presentation) files is this:
One ends with an "S". The other ends with a "T".
PPT
PPS
That's it. Otherwise, they're identical files.
A PPS is just a PPT file with a different file extension that tells PowerPoint "Open me directly into slide show view, not editing view." You can "convert" from one to the other simply by renaming the files. You need the same software to view either one.