CUPS
also: Common Unix Printing System, cupsd
CUPS (Common Unix Printing System) is the standard printing service on Linux and macOS that manages print queues, drivers, and communication between applications and printers.
CUPS is a modular printing system that acts as an intermediary between your applications and physical or network printers. It handles print job queuing, scheduling, and routing to the appropriate printer driver, allowing multiple users to share printers seamlessly.
CUPS uses the Internet Printing Protocol (IPP) and provides a web-based administration interface (typically at http://localhost:631) where you can manage printers, view print jobs, and configure settings. Most Linux distributions use CUPS as their default printing backend.
For example, when you print from a document editor, CUPS intercepts the job, converts it to the printer's native format using the appropriate driver, and queues it for output. You can manage jobs from the command line with tools like lp, lpr, and lpstat.