Hostnames

In short: The name of a single device or service within a network, e.g. server1 or mail.emzett-digital.com.

In more detail: A hostname can be local (only valid within your own network) or public as part of a fully qualified domain (FQDN). It’s mapped to an IP address via DNS or local name resolution (e.g. /etc/hosts).

In Depth

The term “hostname” is used in two slightly different meanings:

1. Local device name: the name a machine gives itself (e.g. visible via the hostname command on the command line) — only relevant within your own network, not publicly resolvable via DNS unless explicitly configured for that.
2. Public hostname (FQDN): a fully qualified name like mail.emzett-digital.com, publicly resolvable to an IP address via DNS.

For local name resolution without a DNS server, most operating systems use the file /etc/hosts (Linux/macOS) or C:\Windows\System32\drivers\etc\hosts (Windows) — hostname-to-IP mappings can be manually stored there, checked even before any real DNS query. This is used, for example, for local testing, to redirect a domain to a different server as a test, without changing the real DNS records.

See also: Domain, DNS Records