It is very difficult to remember a set of numbers(IP
address) to connect to the Internet.The Domain Naming
Service(DNS) is used to overcome this problem.It maps one
particular IP address to a string of characters.
  FOr example, www.allinterview.com implies com is the
domain name reserved for commercial sites,allinterview is
the name of  the company and www is the name of the specific
computer,which is allinterview's server.