"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. (...) 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," explains Google.
{ Thanks, Venkat. }