TCP\IP under Windows NT allows a computer to communicate over a network with another computer by using either an IP address, a host name, or a NetBIOS name. However, when one computer attempts to communicate with another computer using one of these three naming conventions, that name must ultimately be resolved to a hardware IP address. The Hosts file is used when a computer is unable to ping another computer by computer name, but can ping by IP address.
Opening the Hosts File
Modifying the Hosts File