Quality of Service - network management technique for prioritizing certain types of traffic. Like having express lanes for emergency vehicles while regular traffic uses standard lanes.
Video conferencing applications use QoS to ensure voice and video data gets priority over file downloads.
QoS (Quality of Service) is a networking capability (not a single cloud service) implemented across routers, switches, firewalls, SD-WAN, and some cloud networking features. Cloud providers offer building blocks (e.g., traffic shaping, priority queuing, bandwidth controls, and private connectivity), but end-to-end QoS typically requires configuration on your network devices and sometimes your OS/application.