The print spooler is the Windows service that accepts print jobs from applications, stores them in a queue and hands them in order to the printer driver and device, so applications can carry on while printing proceeds.
In practice
Print a long report and the application finishes almost immediately while pages keep emerging for minutes. The spooler is holding the job, feeding it through the printer driver and tracking its progress, which you can watch in the print queue window.
Common confusion
The spooler is not the printer driver; it manages jobs while the driver converts their content. It also is not the printer's own memory, although printers buffer data too. A stuck job may reflect the spooler, the driver, the connection or the device.
Why it matters to readers
Knowing the spooler's role makes the print queue far easier to read and clarifies which part of the chain a status message describes.
A closer look
The spooler can also hold jobs for printers that are temporarily unavailable, such as a networked printer that is switched off. Those jobs wait until the printer returns or until they are cancelled. Because the spooler is a shared service, a problem with one job can delay others behind it, which is why the queue window lists everything in order.
