Postscript in a nutshell:
Adobe invented Postscript, a Page Description
Language. This language describes all the contents of a page using
text. This text is quite similar to programming and formatting languages
vector formulas and the bitmap, or raster, graphics are described
pixel by pixel.
Graphic applications speak Postscript. Quark,
Illustrator, Pagemaker, etc. create pages with Postscript.
The raster image will be printed by the output device connected to the RIP. The RIP must make the raster page image to the same resolution as that device; for example, the HP Laserwriter makes 600 spots of toner every inch so the raster image will contain 600 pixels or spots per inch.
The imaging device is a machine which makes marks onto paper or film or plates. These marks may be tiny spots of toner powder, microscopic laser beams exposing photographic films or plates, or little squirts of ink in an inkjet printer. Imaging devices lay down row upon row of these ultra tiny marks to build the raster image we see as the graphic page.
They are so small that it takes hundreds of them to make just one halftone dot. It is as if the type and halftones are in our world and the imagesetter dots are from Whoville
Some people deliver the Postscript file to the print shop and the printers send the file into their imagesetter to create the film or plates. This can save time and eliminate errors if, and this is a big IF, the file has been prepared perfectly. The printer cant make any changes to the Postscript file.
The most common use of saved Postscript page descriptions is in the creation of PDF documents. The Acrobat Distiller processes the information into Acrobat PDF documents. These PDF files can be read by any computer with the Acrobat Reader installed. Acrobat Reader is a free program made available for all the popular operating systems.