The tool shows Your computer's local IP address, Your public IP address and Your IPv6 address (if has). The tool only support Chrome Firefox who is implemented with WebRTC.
If your computer is behind a router or hardware firewall then your computer's IP address is a local IP address, it is only valid in your own local network. If you want to suffer on internet, the machine will see the IP address assigned to your router, the IP address is Public IP or exteranl IP.