Hosts file

A "hosts" file is text file, found on Unix, Linux, Mac and Windows operating systems. It matches IP Addresses with domain names. This allows users to bypass information found in DNS. Users usually wish to do this either to mimic a domain on their local network, or to allow their computer to find a new domain location before DNS servers have updated themselves.

Mac and Linux

• The file is located at /etc/hosts and can be edited by hand

WIndows

• New windows systems locate it at %SystemRoot%\system32\drivers\etc\hosts

More info

• Wikipedia