Open it up with a text editor and it will be obvious
Robbe Morris replied to Vinod Srinivasan on 12-Jan-10 01:19 PM
It gives the local pc a way to map ip addressed to domain names. This can override dns settings from a central server.
mv ark replied to Vinod Srinivasan on 14-Jan-10 12:35 AM
This Hosts file contains the mappings of IP addresses to host names. You can use this file to block sites. Add the URL of the website you want to block to the Windows HOSTS file and set it to a dummy address (127.0.0.1). For instance, you can block IFRAME based ads using this technique - http://mvark.blogspot.com/2007/02/how-to-block-iframe-based-ads.html
The file is present at this path: Windows\System32\drivers\etc