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The facts

Most Mac applications print by sending a series of QuickDraw commands to the Print Manager, which uses the currently-selected printer to decide where and what it should do with the user's print job. Windows prints in a similar way, but it uses a different native print command language.

If a PostScript printer is selected, the Print Manager translates the print job into a PostScript program - a mathematical representation of the page - and sends it to the PostScript device. Once the PostScript code is received by the printer, either via an Ethernet or wireless network or a direct USB connection, it is translated by the PostScript interpreter. This converts the mathematical page description into a bitmap (dot pattern) at the printer's native resolution. This PostScript interpreter is basically a program stored in the printer's ROM, which can either be true PostScript (made by Adobe) or a clone. These days, the practical difference between Adobe PostScript and clone PostScript is generally negligible.

The program runs the PostScript program on the printer's microprocessor, usually a Risc chip made by Intel or AMD. Processing the PostScript image takes up most of the printing process time. Printers with high resolutions generally take longer to process images than their lower-resolution counterparts since they have more information to process; they have to build a higher resolution bitmap image of the page.

The laser printing works by using a laser diode to shine a light source onto a rotating mirror. By being switched on and off and using a rotating polygonal mirror, the light source draws a precise image of the page on the photoconductive drum. The areas of the drum which are exposed to the light become positively charged and attract the negatively charged toner from the toner reservoir. The positively-charged paper then attracts the negative toner from the drum in the shape of the image to be printed. The paper runs past a discharge brush to neutralise the charge and then through the fuser assembly, where it is 'fixed' to the paper using heat. This is generally around 160° celcius; hot enough to burn the paper if it wasn't so localised and brief.