LAN means Local Area Network. This would be the network inside your home or business that connects your shared resources and Internet connection. The most common LAN IP address configurations are in the 192.168.xxx.xxx range. They would be called your Internal IP addresses.
WAN means Wide Area Network. This would be your Internet Service Providers Network. Many Routers label one of the Ethernet ports "Internet", some others more correctly label it "WAN". The WAN IP address would be your External IP address, the one you see on our home page