What Is A Loopback Address?
A loopback address is an IP address which a device can send signals to which will send signals back to the same device. In otherwords, it's a shortcut for your computer to refer to itself.
In IPv4 the loopback address is 127.0.0.1
In IPv6 the loopback address is ::1
The loopback address is often given the alias localhost for more convenient usage during development.