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 the name of a DNS domain, separated from the host specific label by a period (dot). In the latter form, a hostname is also called a domain name. If the domain name is completely specified including a top-level domain of the Internet, the hostname is said to be a fully qualified domain name (FQDN).
Hostnames that include DNS domains are often stored in the Domain Name System together with IP addresses of the host they represent for the purpose of mapping the hostname to an address, or the reverse process.