Every website on the Internet has an address called an IP address. IP addresses take the form: 111.111.111.111. In the General case is 4 numbers, called octets, separated by periods. After the last octet of the dot is not needed. The number can be from 0 to 255.
Please note that when you try to access the site, we recruit not the IP address and domain name. For example mail.ru, yandex.ru, rambler.ru and so on. Isn't this the name to remember is much lighter than some number sequence?
In order to maintain a database of correspondence between IP addresses and domain names were invented DNS (Domain Name System - DNS). This system converts domain names to IP addresses and performs reverse conversion from IP address to domain name. The DNS server address can register in the settings of the Internet connection. It can be issued automatically. If the DNS server for some reason failed, the Internet connection will not be affected, but any domain name can not be resolved to an IP address. Simply put, when typing the domain name of any website in a browser, the user will be error.
DNS is very important in the functioning of the Internet. If it were not for this system, the role of domains, in fact, abolished. Left to some IP addresses which are to pass each other comfortably, and remember even 1 address is much harder than to remember the name of the site.