# Domain

*Internet standard*. A human-readable branding for an individual or organization's presense on the internet. [RFC 1034][rfc1034] defines domains and the [Domain Name System (DNS)][dns].

This differs from a [fully qualified domain name (FQDN)][fqdn]. An FQDN includes both a hostname and a domain, which resolve to an IP address.

An organization uses their domain to associate any internet presence to their organization from websites like `example.com` to email addresses like `alex@example.com`.

A domain covers a domain name space: all internet hosts that an organization manages.

To learn more, see the Twilio [Email Infrastructure Guide][].

[Email Infrastructure Guide]: https://www.twilio.com/en-us/resource-center/the-email-infrastructure-guide-build-it-or-buy-it

[rfc1034]: https://datatracker.ietf.org/doc/html/rfc1034

[dns]: /docs/sendgrid/glossary/dns

[fqdn]: /docs/sendgrid/glossary/fqdn