From click here
"MicroSoft Powerpoint slide show presentation. Double-clicking on this file will cause the slide show to run. (Your entire screen will go blank and soon be filled by the first slide. Left-click with your mouse to progress through the slides; hit Escape on your keyboard at any time to exit.) .pps files are often distributed by e-mail."
I strongly recommend that you virus check this file, particularly if it's from an unknown source, before even considering whether to open it.