IDN (Internationalized Domain Names - Domain Names in National Languages) are domains that have non-Latin characters of national alphabets, for example:
Due to technical limitations, domain names cannot contain non-Latin characters, so special standards RFC 3490, RFC 3491, RFC 3492 and RFC 3454 have been developed to overcome this restriction, according to which such names must be converted into a set of English letters, numbers and hyphens, and at the beginning of such a transformed name a special prefix "xn--" is written. This conversion is called Punycode. It allows you to encode non-Latin names in the national alphabet with ASCII characters.
The conversion process is taken over by the visitor's browser. Therefore, entering "приклад.іспит" and "xn-e1afmkfd.xn-80akhbyknj4f" in the browser line is the same for modern browsers. Only the second option is stored in DNS server databases. In fact, domain names in national languages are aliases for names that begin with "xn--".