A registered port is a network port (a sub-address defined within the Internet Protocol, in the range 1–65535) assigned by the Internet Assigned Numbers Authority (IANA) (or by Internet Corporation for Assigned Names and Numbers (ICANN) before March 21, 2001) for use with a certain protocol or application.
Ports with numbers lower than those of the registered ports are called well-known ports; ports with numbers greater than those of the registered ports are called dynamic and/or private ports.
References
Registered port Wikipedia(Text) CC BY-SA