That means any packet sent to any of those addresses (127.0.0.1 through 127.255.255.255) is looped back. The address 127.0.0.1 is the standard address normally used for IPv4 loopback traffic; the rest are not supported on all operating systems, (and most people don't know of their existence). However they can be used to set up multiple servers on the local machine, all listening on the same port.