Every computer in the Internet receives an unique address which consists of four number blocks, the "IP address". Example: "123.132.1.67". Because these numbers are hard to remember, there is, in addition, the "domain name system", briefly "DNS". Thereby it becomes possible to use nearly any domain names instead of the IP address. If e.g., the domain www.example.com is entered in the browser, the DNS server is asked at which IP address the corresponding web server is accessible, and thereafter the browser sends its inquiries to this numerical IP address. So before a domain name can be used, it must be entered on a domain name server.