ENUM is a mechanism for mapping telephone (E.164) number to Internet resource addreesses,and it is an abbreviation of Electronic NUmber Mapping

• Internet resource addresses are specified as URIs.
• Mapping is performed by DNS lookup
• end users (Applications) can select URI according to their preference
• standerdization by cooperation of IETF and ITU

ENUM is not:

• a directory
• a search service
• a transport service
• a telephony service or voice encoding method
• a rendezvous protocol