In computer networking, a hostname (archaically nodename[1]) is a label that is assigned to a device connected to a computer network and that is used to identify the device in various forms of electronic communication, such as the World Wide Web.
Hostnames may be simple names consisting of a single word or phrase, or they may be structured.
This kind of hostname is translated into an IP address via the local hosts file, or the DNS resolver.
[4] The Internet standards (Request for Comments) for protocols specify that labels may contain only the ASCII letters a through z (in a case-insensitive manner), the digits 0 through 9, and the hyphen-minus character ('-').
The original specification of hostnames required that labels start with an alpha character and not end with a hyphen.
[8][9][10] Systems such as DomainKeys and service records use the underscore as a means to assure that their special character is not confused with hostnames.
This is used by RFC 7816 to reduce the amount of information that is made available to intermediate DNS servers during an iterative query.
Depending on the operating system DNS software implementation, an unqualified hostname may be automatically combined with a default domain name configured into the system in order to complete the fully qualified domain name.