What is Localhost Loopback and 127.0.0.0

LocalHost
Localhost is the standard hostname given to the address of the loopback network interface (usually 127.0.0.1). Simply LocalHost means this computer, the computer on which you are working.Localhost as a hostname translates to an IPv4 address in the 127.0.0.0/8 (loopback), usually 127.0.0.1, or ::1 in IPv6.

LoopBack
Loopback (loop-back) describes ways of routing electronic signals, digital data streams, or flows of items from their originating facility back to the source without intentional processing or modification. This is primarily a means of testing the transmission or transportation infrastructure.

In TCP/IP a loopback device is a virtual network interface implemented in software only and not connected to any hardware, but which is fully integrated into the computer system’s internal network infrastructure. Any traffic that a computer program sends to the loopback interface is immediately received on the same interface.

Correspondingly, the Internet Protocol (IP) specifies a loopback network. In IPv4 this is the network with the CIDR prefix 127/8. The most commonly used IP address on the loopback device is 127.0.0.1 for IPv4, although any address in the range 127.0.0.0 to 127.255.255.255 is mapped to it.
IPv6 designates only a single address for this function, 0:0:0:0:0:0:0:1 (also written as ::1), having the ::1/128 prefix.

Uses of LoopBack
A loopback interface has several uses. It may be used by network client software on a computer to communicate with Server software on the same computer, namely on a computer running a web server, pointing a web browser to the URLs http://127.0.0.1/ or http://localhost/ will access that computer’s own web site. This works without any actual network connection–so it is useful for testing services without exposing them to security risks from remote network access.
Also, pinging the loopback interface is a basic test of the functionality of the IP stack in the operating system.