It is a programming language which defines precisely how a printed page will appear. Postscript was invented by the company Adobe in 1985. Apple has also contributed to spread this standard, which today dominates the graphics field.
Postscript is a common denominator for a number of printers and image producing equipment.
One of the advantages is that PS works independently from the resolution. A print job from a 600 dpi HP4M laser printer can thus be sent to any other printer and possibly be printed with 2400 dpi. Many laser printers are available today with built-in Postscript at a reasonable price. Steve Jobs attempted in his NeXT computers to make Postscript into a screen language.