IANA operates and coordinates the central root zone of the domain name system (DNS), whose levels (top-level domain, second-level domain, and subdomain) make up the complete domain names. In this context, IANA also manages the database with all top-level domains (TLDs), the last part of the complete domain name. It also coordinates the .int and .arpa TLDs. The TLD “int” is reserved for intergovernmental contract organizations, while the TLD “arpa” is used only for technical infrastructure purposes.
In addition, IANA maintains the central collection of permissible internationalized domain names. IDNs, also colloquially referred to as special character domains, allow umlauts, diacritic characters (small characters attached to letters that indicate pronunciation or tone), or letters from alphabets other than Latin to be integrated into the domain name. Originally, this kind of character was not provided for in the DNS. To cope with the growth and the resulting globalization of the internet, the use of special characters was subsequently made possible by the internet standard “Internationalizing Domain Names in Applications” (IDNA).