WAN
Short for Wide Area Network, WAN is a collection of computers and network resources connected via a network over a geographic area. Wide-Area Networks are commonly connected either through the Internet or special arrangements made with phone companies or other service providers. A WAN is different from a MAN because of the distance between each of the networks. In a WAN, one network may be anywhere from several hundred miles away, to across the globe in a different country.
For home routers the port the router connects to your Internet connection is often labeled as a WAN, Network or Internet port, since it is what allows your home network to communicate with the Internet network.
Also see: Enterprise-wide network, LAN, MAN, Networking definitions, WEP, Wi-Fi