Domain Name System and DNS Servers

You use one other type of Internet server almost every time that you request information from an Internet host. A Domain Name system (DNS) server translates between the numeric IP addresses that identify each host computer on the Internet and the corresponding names. People prefer use host names because they are easier to type and remember but actual Internet communications use the numeric addresses. For example if your browser requests a web page from the DatorLab web site, which has the host name www.datorlab.com, a DNS server translates that name to abc.def.ghi.jkl, one of Lab's web servers, and then sends the request to that IP address.
Your ISP provides a DNS server to handle domain name translations. If the DNS server isn't working properly, or you have configured your computer with the wrong IP address for the DNS server, your computer can't find any of the computers on the Internet that you specify by host name. It has no way to translate host names to IP addresses. You may see error messages such as "Unable to locate host" or "Server does not have a DNS entry".