INFO

Types of domains

Top-level domain (TLD) is an internet domain at the top level Internet domain tree. In the domain name is top-level domain listed at the end (for example in cases of offaxis.cz, stretchfolie.cz, zapo-obchod.cz, vlanskroune.cz is TLD -.cz). The TLD describes the core group of domain names such as domain names of the state. The TLD are set by the Internet standardization organization IANA. There are following three types of TLDs:

Country-code TLD (ccTLD) associate domains of one state. Their name are two-letter with few exceptions corresponding to a country code in ISO 3166-1, for example, *.cz for the Czech Republic.
Generic TLD (gTLD) associate general domains (for example *.org for nonprofit organizations), not associated with one particular state (with the exception TLD *.mil and *.gov, which are reserved for the military respectively government computer networks in USA).
Infrastructure TLDs are used for the internal mechanisms of the Internet. Currently there is one such a TLD: ARPA, used by DNS.

Country-code TLD (ccTLD) is a top-level domain for the general domains of the state or the dependent territory. Its name is a two-letter and exceptions corresponding country code in ISO 3166-1. For example domain *.com is designed for computer networks in the Czech Republic. In each state the domain administrator of the ccTLD determines the rules by which the domain names in the TLD are assigned. Some states allow registration of names in the ccTLD to any candidate, regardless of whether the candidate has something relevant in common. Among these states and territories belongs CR with its domain *.cz. Other countries and dependent territories allow registration of domain in the TLD only to citizens and businesses of the country. Good example is Canada (*.ca), Mongolia (*.mn) and Slovakia (*.sk). Most national countries use code domain in accordance with ISO 3166-1. Some ccTLD do not comply with this convention.

Domain Name

Internet domain (domain name) is a unique name (identifier) of computers or computer networks that are connected to the Internet. An example of a domain name is www.offaxis.cz. A domain name consists of a sequence of several parts separated by dots. The parts are sorted by generality (my.offaxis.cz): the first part (my.) is the most concrete it may describe a specific computer, the last part (*.cz) is the most general describing a large group of computers and networks. The last part is called top-level domain (TLD), as you know, and describes distribution of the country and the general category of organizations. Individual parts are sometimes numbered (again from the back), so *.cz is a first level domain, offaxis.cz is the second level and my.offaxis.cz is the third level domain etc.

In the domain names can be used only a small part of the ASCII characters: characters English alphabet, numbers and dash (each part of the name must not begin or end with a hyphen). Names are not case-sensitive (www.offaxis.cz describes the same computer as WWW.offaxis.Cz) and each part of the name can be up to 63 characters long. Length of the name can be up to 255 (number of parts is not limited, that means a name may be theoretically composed of 127 parts of the single letter). Thank to the expansion of the Internet to countries that use different fonts has begun relatively recently to bring to life IDN system that allows the use of arbitrary Unicode characters in domain names. For reasons of backward compatibility, however, other characters can not be directly used in the present system, because the "standard" characters before using a special procedure to convert a sequence of "normal" characters in a special code.

Domain´s alias means that at the same server lead lots of domains. It can be used offaxis.cz as well as offaxis.eu and both refer to the same area for pages on a server it means that same presentation will be displayed.
Detailed information about their operators is kept for all registered domains. For this purpose exists database called whois from which it can be freely obtained using a variety of tools. This information can also be used to determine whether the domain is free or not.
Note: The information on this page is taken from www.wikipedia.org, www.nic.cz.