Microsoft Knowledge Base Article 233039 contains the following summary:

Included in the Quality of Service (QoS) Internetwork architecture is a discipline sometimes called Queue Management. Queuing is a technique used in internetwork devices such as routers or switches during periods of congestion. Packets are held in the queues for subsequent processing. After being processed by the router, the packets are then sent to their destination based on priority (IP Precedence, 802.1P).