The two IP addresses you see are for two different networks, your local network and the IP address used for your local network to access the Internet. Long story short, your LAN IP address is a local IP address determined by your router (or you if you choose to manually set it) and is used to specify devices on your local network. The address you get from whatismyip.com is the address your network gets from the Internet Service Provider and devices on your local network to access the Internet. In practice this means that on your local network each machine will have a different local IP address, but the same remote IP address.