A PPS file is a Powerpoint Slide Show, so a PowerPoint slideshow. The PPS format is the standard presentation format of Microsoft PowerPoint version 97 - 2003. With the 2007 version, Microsoft has introduced the new ppsx format. Of course you can also read PPS files with the new program versions.
Just like a ppt file, a PPS file contains slides that contain images, text, animation, and audio, among other things. A PPS file differs mainly in two things from ppt. On the one hand, it is not editable and on the other hand, if a program for displaying PowerPoint files is installed, the slideshow starts immediately.
This makes the PPS format ideal for presentations. In addition, there are converters that can convert PPS files into a executable (.Exe) file or various movie formats, such as Flash, avi or MP4. These files can then be started immediately and do not require an installed PowerPoint program. For the film formats, of course, a player is required. In general, all programs that can read ppt files can also handle PPS files.