Hostname

A hostname 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, e-mail or Usenet. Hostnames may be simple names consisting of a single word or phrase, or they may have appended a domain name, which is a name in a Domain Name System (DNS), separated from the host specific label by a period (dot). In the latter form, the hostname is also called a domain name. If the domain name is completely specified including a top-level domain of the Internet, then the hostname is said to be a fully qualified domain name (FQDN).

Example: 'saturn' and 'jupiter' could be the hostnames of a couple of devices connected to a network called Alpha. Within Alpha the devices are reached by their hostname. Alpha could be configured so that its domain name is 'alpha' (in lower case letters). In that case, the mentioned devices' hostnames, including the domain-name, would be 'saturn.alpha' and 'jupiter.alpha', respectively. With these names they could be reached in a private network of networks, each with its own domain name. If alpha is registered and can be reached as alpha.net on the Internet, then the fully qualified domain names for the devices would be 'saturn.alpha.net' and 'jupiter.alpha.net'.

Hostnames that include DNS domains are often stored in the Domain Name System together with the IP addresses of the host they represent for the purpose of mapping the hostname to an address, or the reverse process.