Are there guidlines for Domainnames?

Any name can be taken for a Domain. It makes sense to choose, for example, the name of the company as the Domainname. Basically the 26 letters of the alphabet and the numerals 0 to 9 can be taken for the name. You have the possibility, however, to use further characters by Internationalized Domain Names. Internationalized Domain Names are extensions which vary in the different Top-Level-Domains. Country-Domains are mostly extended by country-specific characters. For example, ‚ä’, ‚ö’ and ‚ü’ are possible for .de-Domains.There is no distinction between upper and lower case.