An acronym for Simultaneous Peripheral Operations On-Line, spooling refers to putting jobs in a buffer, a special area in memory or on a disk, where a device can access them when it is ready. Spooling is useful because different devices access data at different rates. The buffer provides a waiting station where data can rest while the slower device catches up.
The most common spooling application is print spooling. In print spooling, documents are loaded into a buffer (usually an area on a disk), and then the printer pulls them from the buffer at its own rate. Because the documents are in a buffer where they can be accessed by the printer, you can perform other operations on the computer while the printing takes place in the background. Spooling also lets you place a number of print jobs on a queue instead of waiting for each one to finish before proceeding to the next one.