IP addresses are used to communicate on a network. They can be represented in host name form (apple.com, or supersync.com) or by the IP4 standard of 4 numbers 0..255 separated by dots, (192.168.100.1)
Two types of IP addresses are common -- NAT addresses that are only available from inside a firewall or router. This is the most common for home users. For simplicity, a NAT address starts with 192. or 10.
Use the Tools-> Check my IP address menu to get more information about your IP address and whether it is accessible. Use the "Test Connection" button to determine if your server is accessible over the Internet (WAN Access).