A WAN port is an RJ-45 Ethernet port on a router that is wired to a cable, DSL, or FiOS modem. It is used to connect the router to your internet connection, which is the Wide Area Network (WAN) or the internet. The WAN port is usually labeled "Internet" or "WAN" and is separated from the LAN ports on the router. The LAN ports are used to connect local network devices to your home network. The WAN and LAN ports look the same, but they are separated internally with a firewall. The WAN port can only be used to connect the router to the modem and cannot be used for connecting more LAN ports.