Postscript and graphic design

The PostScript language along with PageMaker, the original Apple Macintosh, and the Canon CX laser print engine were technologies and products that came together in the mid-1980s that enabled low-cost, high quality WSYWIG (“What You See Is What You Get”) “desktop” publishing.

PostScript from Adobe was a language with rich graphic operators and scalable, hinted fonts that was not printer or manufacturer-specific. And the same “language” and resources could be used for a wide range of printer products ranging from low resolution laser printers to high resolution imagesetters.

The Apple Macintosh provided an affordable desktop system that could run graphic-arts oriented software such as PageMaker followed by Illustrator, QuarkXPress, and Photoshop.

The Canon CX 300dpi laser print engine was the basis for affordable, high quality laser printers manufactured by QMS, Apple, and HP that were able to all  use the same PostScript page description language.

You ask about PostScript. PostScript was the original basis for PDF, less the programming constructs (loops, variables, etc.) of PostScript. Whereas in the 1990s, graphic arts applications produced PostScript for printing, now such software generally directly produces PDF. Many if not most high end devices can directly process such PDF; for those that don't, the PDF files can be readily opened in Adobe Reader or Acrobat and printed to non-PDF-native printers including PostScript printers.

Generally speaking, though, there is no reason for a graphics designer to know any details about PostScript these days. Working knowledge of PDF, not the internals but what it does and supports, is appropriate!