Printing on a UNIX-like operating system has traditionally given headaches to even experienced sysadmins. The FreeBSD Handbook has a big section on how printers work, and it's well worth reading if you want to become intimate with the innards of printing. Personally, I don't want to struggle with identifying file types, input filters, and output filters; I want to plug in a printer and have the Magical Printer Pixies do all the work for me.