What device is primarily used to connect different networks?

The device primarily used to connect different networks is a router. A router plays a crucial role in networking because it directs data packets between multiple networks, making it essential for inter-network communication. It analyzes the destination IP address of packets and uses routing tables and protocols to determine the best path for forwarding the packets to their eventual destination, which may reside on a different network.

Routers are capable of managing traffic efficiently between various networks and can connect diverse network types, such as local area networks (LANs) and wide area networks (WANs). This functionality allows them to serve as gateways, facilitating communication between networks that may use different technologies, protocols, or architectures.

In contrast, a switch primarily operates within a single network, connecting devices within that network to communicate effectively. A hub also connects devices within a network but does this in a more simplistic and less efficient manner by broadcasting data to all connected devices. Finally, a bridge connects two segments of a network but does not connect different networks at a higher level like a router does. Thus, the router is the correct choice for connecting different networks.