Definition - What does Loopback Address mean?
A loopback address is a type of IP address that is used to test the communication or transportation medium on a local network card and/or for testing network applications. Data packets sent on a loopback address are re-routed back to the orginating node without any alteration or modification.
Techopedia explains Loopback Address
In IPv4, 127.0.0.1 is the most commonly used loopback address, however, this can range be extended to 127.255.255.255.