Internationalized Domain Name
IDN (Internationalized Domain Name) represents an Internet domain name that uses the latest ICANN standards that have the objective to modify the current DNS protocols and standards to support multiple scripts and languages(non-ASCII characters).
The Internationalized domain name (IDN) can also be perceived as the label displayed in a software application, in an alphabet or language-specific script. The IDNs are stored in DNS as ASCII strings. The DNS performs look-up services to ensure the translation of user-friendly names to locate the Internet resources, and it is restricted to use ASCII characters as a limitation for acceptable domains. Based on these facts, the IDNs are a solution to ensure the translation names written by means of native-language scripts into ASCII text being compatible with DNS.
The IDN was proposed by Martin Dürst in 1996 and implemented only in 1998 by Tan Juay Kwang and Leong Kok Yong. Later on, the IDNA system (Internationalizing Domain Names in Applications) was adopted and implemented in some top-level domain names. According to the IDNA system, an "internationalized domain name" signifies any domain name which contains labels on which the IDNA ASCII algorithm could be applied.
ICANN and IDN
According to ICANN,Internationalized Domain Names (IDNs) are domain names represented by local language characters.  These types of domain names could either contain non-ASCII scripts characters or letters.
An important milestone in the development of IDN TLD was the ICANN meeting from Korea which took place in the period 26-30 October, 2009. As a result of this meeting, the ICANN Board presented its approval related to the IDN ccTLD Fast Track Process that will enable countries that use language-based-scripts to offer domain names with non-Latin characters. 
In this way, starting with October, 2009, ICANN has accepted the development of IDN ccTLDs (internationalized country code top-level domain names) on the Internet using IDNA standards. The first IDN ccTLDs were successfully installed in DNS root zone in May, 2010.
How to register an IDN?
There are plenty of companies and partners that offer the possibility to register an IDN using the native language characters. During the registration process, the language should be selected and then the domain name typed. The Internationalized Domain Names can contain diacritics and non-Latin characters. The syntax designed for the used of IDNA is known as "Punycode". The non-ASCII characters are transformed into a specific format containing only ASCII characters and then a unique identification is processed for the domain name. 
In order to the characters used in a IDN various changes and specific settings should be performed in the Web browser or the installation of foreign language pack should be required.