From iA wiki
Acronym: Internet Assigned Numbers Authority
Under charter by ISOC this authority is dedicated to preserving the central coordinating functions of the global Internet for the public good. This organisation is responsible for maintaining the infrastructure such as Domain Name Services and IP Address Services.
The IANA houses the many unique parameters and protocol values necessary for operation of the Internet and its future development. Types of numbers range from unique port assignments to the registration of character sets.
IANA asigns blocks of IP addresses to ISP's in North America. European ip assignments have been delegated to RIPE. Asia Pacific area IP assignments are done by APNIC or regional registrys it has delegated to such as KORNIC.