Freename supports the following alphabets that can be used for registration of SLDs and TLDs:
The Unicode Standard provides a unique number for every character, no matter what platform, device, application or language. It has been adopted by all modern software providers and now allows data to be transported through many different platforms, devices and applications without corruption.
Support of Unicode forms the foundation for the representation of languages and symbols in all major operating systems, search engines, browsers, laptops, and smart phones — plus the Internet and World Wide Web (URLs, HTML, XML, CSS, JSON, etc.).
Despite Unicode standard Freename converts each string in a Punycode string, as used by web2 domain providers.
Punycode is a representation of Unicode with the limited ASCII character subset used for Internet hostnames.
Learn more about Unicode here: https://en.wikipedia.org/wiki/Unicode
For experts who want to dig deeper here in addition information about Punycode: https://en.wikipedia.org/wiki/Punycode
Here you will find some good Unicode compilations: