Domain Name System (DNS)
The Domain Name System (DNS) is vital in order to ensure that the desired internet websites can be reached and that e-mails find their way to the addressee. Via DNS the names (domains) are translated into IP-addresses and vice versa.
IP-addresses are used for the identification of computers on the internet. They consist of number strings separated by dots (e.g. 131.130.1.11). In technical terms, these IP-addresses would be sufficient to address websites and send e-mails. However, IP-addresses are not user-friendly, because they are only hard to remember and do not contain any additional information. As a result, a name structure was introduced in order to simplify the internet navigation: the Domain Name System (DNS).
The DNS is a hierarchical, peripheral system for the administration of names, which allocates responsibilities and ensures the uniqueness of names. This applies to both IP-addresses and DNS names. The DNS is based on a tree-like structure of the entire name area, whose root branches out to different branches called Top Level Domains (TLD). These TLDs are split up into further branches themselves, which are called Second Level Domains.
The international organisation ICANN 
(Internet Corporation For Assigned Names and Numbers) is responsible for the root level of the DNS and coordinates the administration of the appendant root-nameservers. The responisbility for the administration of the country-specific Top Level Domains has been taken over by organisations that have been established by the local internet communities - which is nic.at in Austria.