The device primarily used to route traffic on the Internet is the router. Routers connect multiple networks, directing data packets between them to ensure that information reaches its appropriate destination. They utilize routing tables and protocols, such as TCP/IP, to determine the most efficient pathways. Modern routers can also provide additional functionalities, including firewall protection, traffic management, and network address translation (NAT). As critical components in both home and enterprise environments, routers facilitate seamless internet connectivity and communication.