A subnetwork is a smaller network that is part of a larger network. It allows for better organization and management of devices, making it easier to control traffic and improve security. Subnetworks are commonly used in computer networks to divide a larger network into manageable sections. In the context of the Internet, subnetworks help optimize performance by reducing congestion. Each subnetwork can have its own set of rules and configurations, which can be tailored to specific needs. This is particularly useful for organizations that require different levels of access and security for various departments or teams, such as IT and HR.