Maria Teresa Taylor Oliver wrote:
As everyone else already said, PS stands for PostScript, which is a printer language. A PS file is a "raw" file, "printed" by a PostScript printer to be converted to a final PDF file, which you can then open with Adobe Acrobat Reader.
You can open PS files with Adobe Acrobat Distiller, which processes them, and then converts them to PDF.
Hope that helps
A short history of Adobe PostScript can be found here: