Which device connects multiple networks together and relays messages to computers with appropriate IP addresses?

The device that connects multiple networks together and relays messages to computers with appropriate IP addresses is a router. Routers work by examining the destination IP addresses of incoming data packets and deciding the best path for them to reach their intended destination.

Routers operate at the network layer of the OSI model, enabling them to route data between different networks, which could include home networks, office networks, and the broader internet. They use routing tables and protocols to determine the most efficient path for data transmission, ensuring that messages are sent to the correct devices based on their unique IP addresses.

In contrast, a modem primarily connects a single network to the internet, converting digital data from a computer into an analog signal for transmission over phone lines or cable systems, but it does not manage multiple network connections. A network switch operates within a single network, forwarding data to devices based on their MAC addresses, and does not connect different networks. A wireless access point extends a wired network by providing a Wi-Fi connection for wireless devices, but it also does not function to relay messages between different networks in the same way that a router does.