This allows a user to refer to a host by a symbolic name instead of an Internet address.
Aliases are other names by which a host is known.
They can substitute for the official host name in most commands. If your system is in a domain naming environment, an official host name consists of the full domain extended host name. Trailing blanks are allowed at the end of a line. Host names can contain any printable character other than a white space, newline, or comment character.