CUPS provides a portable printing layer for UNIX-based operating
systems. It has been developed by Easy Software Products to promote a
standard printing solution for all UNIX vendors and users. 

CUPS uses the Internet Printing Protocol ("IPP") as the basis for
managing print jobs and queues. The Line Printer Daemon ("LPD") Server
Message Block ("SMB"), and AppSocket (a.k.a. JetDirect) protocols are
also supported with reduced functionality. CUPS adds network printer
browsing and PostScript Printer Description ("PPD") based printing
options to support real-world printing under UNIX.

CUPS provides the System V and Berkeley command-line interfaces.

CUPS also supports a customized version of GNU Ghostscript (currently based
off GNU Ghostscript 5.50) and an image file RIP that are used to support
non-PostScript printers. Sample drivers for HP and EPSON printers are included
that use these filters. This software is available in the cups-pstoraster
port.

WWW: http://www.cups.org/
[original text by greid@ukug.uk.freebsd.org]