Just like a street address determines the recipient of a letter, an IP address (short for Internet Protocol address) is used to identify computers on the Internet.
When your computer sends a request, such as a Google query, it tags the request with its IP address in order for the response to be sent back to your computer — just like a return address on a letter. IP addresses are sequences of numbers that are usually displayed in readable notations, such as 172.16.254.1 (for IPv4) and 2001:db8:0:1234:0:567:8:1 (for IPv6).
When you type the query [what is my ip], Google will respond by showing you the IP address of the computer from which the query was received. In the simplest case, this IP address uniquely identifies your computer among all computers on the Internet.
There are, however, several network configurations that may cause Google to receive an IP address that differs from the one assigned to your computer. For example, if you have a home network or a corporate network, devices are usually assigned “internal” IP addresses by a Network Address Translator (NAT) located within your router or modem.
The NAT hides the internal IP addresses from websites, making the entire home network appear to outside computers to have a single, “external” IP address. In this case, we will show you the external IP address assigned to your home. Other network configurations, such as proxies, can also cause the IP address received by Google to differ from the actual IP address of your computer